SQL Server DBA Interview Questions 7

                                          Interview Questions

   1. What are the System Databases in SQL Server 2000/2005? Explain?
 
   2. What is the main Differences between Clustered Index and Non Clustered Index?
  
   3. How to Truncate the Transaction Log?
 
   4. Explain the Difference between Join/Union or Union/Union All?

   5. Difference between  Delete/Truncate or Delete/Drop?

   6. Define Normalization?Explain the Normal Forms?

   7. Define Denormalization?Use of Denormalization?

   8. What is file group?
 
   9. Define Isolation level?How many types of Isolation level?what is the default Isolation level?
 
  10. What is the Difference between SQL Server 2000/ 2005?

  11. What is Deadlock?How to avoid deadlock?

  12. Difference  between locking and Deadlock?
 
  13. Explain Difference between Index Rebuild and Index Defrag?

  14. How to troubleshoot when SQL SERVER is running slow.

  15. what is the difference between Logshipping and Replication.

  16. What is the purpose of Logshipping.

  17. How to troubleshoot when msdb is running slow.

  18. What do u mean by Disaster of Recovery.

  19. what are the default databases.

  20. How to connect to SQL SERVER.

  21. How many types of authentications are there?

  22. Which authentication is the best one(Windows or sql server authentication)?

  23. How to Rebuild Master database?

  24. What is the architecture of Log-shipping?

  25. What is Replication?How many types of Replication are there?

  26. What are the Monitoring tools?

  27. How many backup's are there.What is the difference between full and differential database?

  28. Explain the differences between Database Mirroring and Logshipping?

  29. Explain SQL Profiler?What is the output of SQL Profiler?

  30. Explain Fragmentation?What is Command of Fragmentation?

  31. What do u mean by Index tunning wizard?
 
  32. What do u mean by Checkpoint?

  33. How will we come to know that backup is failed?

  34. what do u mean by DBCC Command?What are the commands u use in ur company?

  35. How to move/copy the data from one database to other database or from  one sever to other server in SQLSERVER?

  36. What is command u use to know the version of SQL SERVER in T-SQL?

  37. What are the TCP/IP protocal in SQL Server?

  38. How  will u troubleshoot if Insallation is not completed properly?

  39. How  will u bring the database if it is in suspect status?

  40. How to troubleshoot if tempdb is full?

SQL Server DBA Interview Questions 6

SQL Server 2005 Interview Questions

• If I want to see what fields a table is made of, and what the sizes of the
fields are, what option do I have to look for?
Sp_Columns ‘TableName’
• What is a query?
A request for information from a database. There are three general methods for posing queries:
# Choosing parameters from a menu: In this method, the database system presents a list of parameters from which you can choose. This is perhaps the easiest way to pose a query because the menus guide you, but it is also the least flexible.
# Query by example (QBE): In this method, the system presents a blank record and lets you specify the fields and values that define the query.
# Query language: Many database systems require you to make requests for information in the form of a stylized query that must be written in a special query language. This is the most complex method because it forces you to learn a specialized language, but it is also the most powerful.
• What is the purpose of the model database?
It works as Template Database for the Create Database Syntax
• What is the purpose of the master database?
Master database keeps the information about sql server configuration, databases users etc
• What is the purpose of the tempdb database?
Tempdb database keeps the information about the temporary objects (#TableName, #Procedure). Also the sorting, DBCC operations are performed in the TempDB
• What is the purpose of the USE command?
Use command is used for to select the database. For i.e Use Database Name
• If you delete a table in the database, will the data in the table be deleted too?
Yes
• What is the Parse Query button used for? How does this help you?
Parse query button is used to check the SQL Query Syntax
• Tables are created in a ____________________ in SQL Server 2005.
resouce database(System Tables)
• What is usually the first word in a SQL query?
SELECT
• Does a SQL Server 2005 SELECT statement require a FROM?
NO
• Can a SELECT statement in SQL Server 2005 be used to make an assignment? Explain with examples.
Yes. Select @MyDate = GetDate()
• What is the ORDER BY used for?
Order By clause is used for sorting records in Ascending or Descending order
• Does ORDER BY actually change the order of the data in the tables or does it just
change the output?
Order By clause change only the output of the data
• What is the default order of an ORDER BY clause?
Ascending Order
• What kind of comparison operators can be used in a WHERE clause?

Operator	Meaning
= (Equals)	Equal to
> (Greater Than)	Greater than
< (Less Than)	Less than
>= (Greater Than or Equal To)	Greater than or equal to
<= (Less Than or Equal To)	Less than or equal to
<> (Not Equal To)	Not equal to
!= (Not Equal To)	Not equal to (not SQL-92 standard)
!< (Not Less Than)	Not less than (not SQL-92 standard)
!> (Not Greater Than)	Not greater than (not SQL-92 standard)

• What are four major operators that can be used to combine conditions on a WHERE
clause?
OR, AND, IN and BETWEEN
•



 What are the logical operators?

Operator	Meaning
ALL	TRUE if all of a set of comparisons are TRUE.
AND	TRUE if both Boolean expressions are TRUE.
ANY	TRUE if any one of a set of comparisons are TRUE.
BETWEEN	TRUE if the operand is within a range.
EXISTS	TRUE if a subquery contains any rows.
IN	TRUE if the operand is equal to one of a list of expressions.
LIKE	TRUE if the operand matches a pattern.
NOT	Reverses the value of any other Boolean operator.
OR	TRUE if either Boolean expression is TRUE.
SOME	TRUE if some of a set of comparisons are TRUE.

•In a WHERE clause, do you need to enclose a text column in quotes? Do you need to enclose a numeric column in quotes?
Enclose Text in Quotes (Yes)
Enclose Number in Quotes (NO)
• Is a null value equal to anything? Can a space in a column be considered a null value? Why or why not?
No NULL value means nothing. We can’t consider space as NULL value.
• Will COUNT(column) include columns with null values in its count?
Yes, it will include the null column in count
• What are column aliases? Why would you want to use column aliases? How can you embed blanks in column aliases?
You can create aliases for column names to make it easier to work with column names, calculations, and summary values. For example, you can create a column alias to:
* Create a column name, such as “Total Amount,” for an expression such as (quantity * unit_price) or for an aggregate function.
* Create a shortened form of a column name, such as “d_id” for “discounts.stor_id.”
After you have defined a column alias, you can use the alias in a Select query to specify query output
• What are table aliases?
Aliases can make it easier to work with table names. Using aliases is helpful when:
* You want to make the statement in the SQL Pane shorter and easier to read.
* You refer to the table name often in your query — such as in qualifying column names — and want to be sure you stay within a specific character-length limit for your query. (Some databases impose a maximum
length for queries.)
* You are working with multiple instances of the same table (such as in a self-join) and need a way to refer to one instance or the other.
• What are table qualifiers? When should table qualifiers be used?
[@table_qualifier =] qualifier
Is the name of the table or view qualifier. qualifier is sysname, with a default of NULL. Various DBMS products support three-part naming for tables (qualifier.owner.name). In SQL Server, this column represents the database name. In some products, it represents the server name of the table’s database environment.
• Are semicolons required at the end of SQL statements in SQL Server 2005?
No it is not required

• Do comments need to go in a special place in SQL Server 2005?
No its not necessary

• When would you use the ROWCOUNT function versus using the WHERE clause?
Returns the number of rows affected by the last statement. If the number of rows is more than 2 billion, use ROWCOUNT_BIG.
Transact-SQL statements can set the value in @@ROWCOUNT in the following ways:
* Set @@ROWCOUNT to the number of rows affected or read. Rows may or may not be sent to the client.
* Preserve @@ROWCOUNT from the previous statement execution.
* Reset @@ROWCOUNT to 0 but do not return the value to the client.
Statements that make a simple assignment always set the @@ROWCOUNT value to 1.

• Is SQL case-sensitive? Is SQL Server 2005 case-sensitive?
No both are not case-sensitive. Case sensitivity depends on the collation you choose.
If you installed SQL Server with the default collation options, you might find that the following queries return the same results:
CREATE TABLE mytable
(
mycolumn VARCHAR(10)
)
GO
SET NOCOUNT ON
INSERT mytable VALUES(’Case’)
GO
SELECT mycolumn FROM mytable WHERE mycolumn=’Case’
SELECT mycolumn FROM mytable WHERE mycolumn=’caSE’
SELECT mycolumn FROM mytable WHERE mycolumn=’case’
You can alter your query by forcing collation at the column level:
SELECT myColumn FROM myTable
WHERE myColumn COLLATE Latin1_General_CS_AS = ‘caSE’
SELECT myColumn FROM myTable
WHERE myColumn COLLATE Latin1_General_CS_AS = ‘case’
SELECT myColumn FROM myTable
WHERE myColumn COLLATE Latin1_General_CS_AS = ‘Case’
– if myColumn has an index, you will likely benefit by adding
– AND myColumn = ‘case’

• What is a synonym? Why would you want to create a synonym?
SYNONYM is a single-part name that can replace a two, three or four-part name in many SQL statements. Using SYNONYMS in RDBMS cuts down on typing.
SYNONYMs can be created for the following objects:
* Table
* View
* Assembly (CLR) Stored Procedure
* Assembly (CLR) Table-valued Function
* Assembly (CLR) Scalar Function
* Assembly Aggregate (CLR) Aggregate Functions
* Replication-filter-procedure
* Extended Stored Procedure
* SQL Scalar Function
* SQL Table-valued Function
* SQL Inline-table-valued Function
* SQL Stored Procedure
Syntax
CREATE SYNONYM [ schema_name_1. ] synonym_name FOR < object >
< object > :: =
{
[ server_name.[ database_name ] . [ schema_name_2 ].| database_name . [ schema_name_2 ].| schema_name_2. ] object_name
}


• Can a synonym name of a table be used instead of a table name in a SELECT statement?
Yes
• Can a synonym of a table be used when you are trying to alter the definition of a table?
Not Sure will try
• Can you type more than one query in the query editor screen at the same time?
Yes we can.
• While you are inserting values into a table with the INSERT INTO .. VALUES option, does the order of the columns in the INSERT statement have to be the same as the order of the columns in the table?
Not Necessary
• While you are inserting values into a table with the INSERT INTO .. SELECT option, does the order of the columns in the INSERT statement have to be the same as the order of the columns in the table?
Yes if you are not specifying the column names in the insert clause, you need to maintain the column order in SELECT statement
• When would you use an INSERT INTO .. SELECT option versus an INSERT INTO .. VALUES option? Give an example of each.
INSERT INTO .. SELECT is used insert data in to table from diffrent tables or condition based insert
INSERT INTO .. VALUES you have to specify the insert values
• What does the UPDATE command do?
Update command will modify the existing record

• Can you change the data type of a column in a table after the table has been created? If so,which command would you use?
Yes we can. Alter Table Modify Column
• Will SQL Server 2005 allow you to reduce the size of a column?
Yes it allows




• What integer data types are available in SQL Server 2005?
Exact-number data types that use integer data.

Data type	Range	Storage
bigint	-2^63 (-9,223,372,036,854,775,808) to 2^63-1 (9,223,372,036,854,775,807)	8 Bytes
int	-2^31 (-2,147,483,648) to 2^31-1 (2,147,483,647)	4 Bytes
smallint	-2^15 (-32,768) to 2^15-1 (32,767)	2 Bytes
tinyint	0 to 255	1 Byte

• What is the default value of an integer data type in SQL Server 2005?
NULL

• What is the difference between a CHAR and a VARCHAR datatype?
CHAR and VARCHAR data types are both non-Unicode character data types with a maximum length of 8,000 characters. The main difference between these 2 data types is that a CHAR data type is fixed-length while a VARCHAR is variable-length. If the number of characters entered in a CHAR data type column is less than the declared column length, spaces are appended to it to fill up the whole length.
Another difference is in the storage size wherein the storage size for CHAR is n bytes while for VARCHAR is the actual length in bytes of the data entered (and not n bytes).
You should use CHAR data type when the data values in a column are expected to be consistently close to the same size. On the other hand, you should use VARCHAR when the data values in a column are expected to vary considerably in size.
• Does Server SQL treat CHAR as a variable-length or fixed-length column?
SQL Server treats CHAR as fixed length column
• If you are going to have too many nulls in a column, what would be the best data type to use?
Variable length columns only use a very small amount of space to store a NULL so VARCHAR datatype is the good option for null values

• When columns are added to existing tables, what do they initially contain?
The column initially contains the NULL values

• What command would you use to add a column to a table in SQL Server?
ALTER TABLE tablename ADD column_name DATATYPE
• Does an index slow down updates on indexed columns?
Yes

• What is a constraint?
Constraints in Microsoft SQL Server 2000/2005 allow us to define the ways in which we can automatically enforce the integrity of a database. Constraints define rules regarding permissible values allowed in columns and are the standard mechanism for enforcing integrity. Using constraints is preferred to using triggers, stored procedures, rules, and defaults, as a method of implementing data integrity rules. The query optimizer also uses constraint definitions to build high-performance query execution plans.
• How many indexes does SQL Server 2005 allow you to have on a table?
250 indices per table
• What command would you use to create an index?
CREAT INDEX INDEXNAME ON TABLE(COLUMN NAME)
• What is the default ordering that will be created by an index (ascending or descending)?
Clustered indexes can be created in SQL Server databases. In such cases the logical order of the index key values will be the same as the physical order of rows in the table.
By default it is ascending order, we can also specify the index order while index creation.
CREATE [ UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX index_name
ON { table | view } ( column [ ASC | DESC ] [ ,...n ] )
• How do you delete an index?
DROP INDEX authors.au_id_ind
• What does the NOT NULL constraint do?
Constrain will not allow NULL values in the column
• What command must you use to include the NOT NULL constraint after a table has already been created?
DEFAULT, WITH CHECK or WITH NOCHECK
• When a PRIMARY KEY constraint is included in a table, what other constraints does this imply?
Unique + NOT NULL

• What is a concatenated primary key?
Each table has one and only one primary key, which can consist of one or many columns. A concatenated primary key comprises two or more columns. In a single table, you might find several columns, or groups of columns, that might serve as a primary key and are called candidate keys. A table can have more than one candidate key, but only one candidate key can become the primary key for that table
• How are the UNIQUE and PRIMARY KEY constraints different?
A UNIQUE constraint is similar to PRIMARY key, but you can have more than one UNIQUE constraint per table.
When you declare a UNIQUE constraint, SQL Server creates a UNIQUE index to speed up the process of searching for duplicates. In this case the index defaults to NONCLUSTERED index, because you can have only one CLUSTERED index per table.
* The number of UNIQUE constraints per table is limited by the number of indexes on the table i.e 249 NONCLUSTERED index and one possible CLUSTERED index.
Contrary to PRIMARY key UNIQUE constraints can accept NULL but just once. If the constraint is defined in a combination of fields, then every field can accept NULL and can have some values on them, as long as the combination values is unique.

• What is a referential integrity constraint? What two keys does the referential integrity constraint usually include?
Referential integrity in a relational database is consistency between coupled tables. Referential integrity is usually enforced by the combination of a primary key or candidate key (alternate key) and a foreign key. For referential integrity to hold, any field in a table that is declared a foreign key can contain only values from a parent table’s primary key or a candidate key. For instance, deleting a record that contains a value referred to by a foreign key in another table would break referential integrity. The relational database management system (RDBMS) enforces referential integrity, normally either by deleting the foreign key rows as well to maintain integrity, or by returning an error and not performing the delete. Which method is used would be determined by the referential integrity constraint, as defined in the data dictionary.

• What is a foreign key?
FOREIGN KEY constraints identify the relationships between tables.
A foreign key in one table points to a candidate key in another table. Foreign keys prevent actions that would leave rows with foreign key values when there are no candidate keys with that value. In the following sample, the order_part table establishes a foreign key referencing the part_sample table defined earlier. Usually, order_part would also have a foreign key against an order table, but this is a simple example.
CREATE TABLE order_part
(order_nmbr int,
part_nmbr int
FOREIGN KEY REFERENCES part_sample(part_nmbr)
ON DELETE NO ACTION,
qty_ordered int)
GO
You cannot insert a row with a foreign key value (except NULL) if there is no candidate key with that value. The ON DELETE clause controls what actions are taken if you attempt to delete a row to which existing foreign keys point. The ON DELETE clause has two options:
NO ACTION specifies that the deletion fails with an error.
CASCADE specifies that all the rows with foreign keys pointing to the deleted row are also deleted.
The ON UPDATE clause defines the actions that are taken if you attempt to update a candidate key value to which existing foreign keys point. It also supports the NO ACTION and CASCADE options.

• What does the ON DELETE CASCADE option do?
ON DELETE CASCADE
Specifies that if an attempt is made to delete a row with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also deleted. If cascading referential actions have also been defined on the target tables, the specified cascading actions are also taken for the rows deleted from those tables.
ON UPDATE CASCADE
Specifies that if an attempt is made to update a key value in a row, where the key value is referenced by foreign keys in existing rows in other tables, all of the foreign key values are also updated to the new value specified for the key. If cascading referential actions have also been defined on the target tables, the specified cascading actions are also taken for the key values updated in those tables.

• What does the ON UPDATE NO ACTION do?
ON DELETE NO ACTION
Specifies that if an attempt is made to delete a row with a key referenced by foreign keys in existing rows in other tables, an error is raised and the DELETE is rolled back.
ON UPDATE NO ACTION
Specifies that if an attempt is made to update a key value in a row whose key is referenced by foreign keys in existing rows in other tables, an error is raised and the UPDATE is rolled back.
• Can you use the ON DELETE and ON UPDATE in the same constraint?
Yes we can.
CREATE TABLE part_sample
(part_nmbr int PRIMARY KEY,
part_name char(30),
part_weight decimal(6,2),
part_color char(15) )
CREATE TABLE order_part
(order_nmbr int,
part_nmbr int
FOREIGN KEY REFERENCES part_sample(part_nmbr)
ON DELETE NO ACTION ON UPDATE NO ACTION,
qty_ordered int)
GO

SQL Server DBA Interview Questions 6 HR GENERAL

·  Tell me about yourself: - The most often asked question in interviews. You need to have a short statement prepared in your mind. Be careful that it does not sound rehearsed. Limit it to work-related items unless instructed otherwise. Talk about things you have done and jobs you have held that relate to the position you are interviewing for. Start with the item farthest back and work up to the present.

·  Why did you leave your last job? - Stay positive regardless of the circumstances. Never refer to a major problem with management and never speak ill of supervisors, co-workers or the organization. If you do, you will be the one looking bad. Keep smiling and talk about leaving for a positive reason such as an opportunity, a chance to do something special or other forward-looking reasons.

·  What experience do you have in this field? - Speak about specifics that relate to the position you are applying for. If you do not have specific experience, get as close as you can.

·  Do you consider yourself successful? - You should always answer yes and briefly explain why. A good explanation is that you have set goals, and you have met some and are on track to achieve the others.

·  What do co-workers say about you? - Be prepared with a quote or two from co-workers. Either a specific statement or a paraphrase will work. Jill Clark, a co-worker at Smith Company, always said I was the hardest workers she had ever known. It is as powerful as Jill having said it at the interview herself.

·  What do you know about this organization? - This question is one reason to do some research on the organization before the interview. Find out where they have been and where they are going. What are the current issues and who are the major players?

·  What have you done to improve your knowledge in the last year? - Try to include improvement activities that relate to the job. A wide variety of activities can be mentioned as positive self-improvement. Have some good ones handy to mention.

·  Are you applying for other jobs? - Be honest but do not spend a lot of time in this area. Keep the focus on this job and what you can do for this organization. Anything else is a distraction.

·  Why do you want to work for this organization? - This may take some thought and certainly, should be based on the research you have done on the organization. Sincerity is extremely important here and will easily be sensed. Relate it to your long-term career goals.

·  Do you know anyone who works for us? - Be aware of the policy on relatives working for the organization. This can affect your answer even though they asked about friends not relatives. Be careful to mention a friend only if they are well thought of.

·  What kind of salary do you need? - A loaded question. A nasty little game that you will probably lose if you answer first. So, do not answer it. Instead, say something like, That’s a tough question. Can you tell me the range for this position? In most cases, the interviewer, taken off guard, will tell you. If not, say that it can depend on the details of the job. Then give a wide range.

·  Are you a team player? - You are, of course, a team player. Be sure to have examples ready. Specifics that show you often perform for the good of the team rather than for yourself are good evidence of your team attitude. Do not brag, just say it in a matter-of-fact tone. This is a key point.

·  How long would you expect to work for us if hired? - Specifics here are not good. Something like this should work: I’d like it to be a long time. Or As long as we both feel I’m doing a good job.

·  Have you ever had to fire anyone? How did you feel about that? - This is serious. Do not make light of it or in any way seem like you like to fire people. At the same time, you will do it when it is the right thing to do. When it comes to the organization versus the individual who has created a harmful situation, you will protect the organization. Remember firing is not the same as layoff or reduction in force.

·  What is your philosophy towards work? - The interviewer is not looking for a long or flowery dissertation here. Do you have strong feelings that the job gets done? Yes. That’s the type of answer that works best here. Short and positive, showing a benefit to the organization.

·  If you had enough money to retire right now, would you? - Answer yes if you would. But since you need to work, this is the type of work you prefer. Do not say yes if you do not mean it.

·  Have you ever been asked to leave a position? - If you have not, say no. If you have, be honest, brief and avoid saying negative things about the people or organization involved.

·  Explain how you would be an asset to this organization - You should be anxious for this question. It gives you a chance to highlight your best points as they relate to the position being discussed. Give a little advance thought to this relationship.

·  Why should we hire you? - Point out how your assets meet what the organization needs. Do not mention any other candidates to make a comparison.

·  Tell me about a suggestion you have made - Have a good one ready. Be sure and use a suggestion that was accepted and was then considered successful. One related to the type of work applied for is a real plus.

·  What irritates you about co-workers? - This is a trap question. Think real hard but fail to come up with anything that irritates you. A short statement that you seem to get along with folks is great.

·  What is your greatest strength? - Numerous answers are good, just stay positive. A few good examples: Your ability to prioritize, Your problem-solving skills, Your ability to work under pressure, Your ability to focus on projects, Your professional expertise, Your leadership skills, Your positive attitude .

·  Tell me about your dream job. - Stay away from a specific job. You cannot win. If you say the job you are contending for is it, you strain credibility. If you say another job is it, you plant the suspicion that you will be dissatisfied with this position if hired. The best is to stay genetic and say something like: A job where I love the work, like the people, can contribute and can’t wait to get to work.

·  Why do you think you would do well at this job? - Give several reasons and include skills, experience and interest.

·  What kind of person would you refuse to work with? - Do not be trivial. It would take disloyalty to the organization, violence or lawbreaking to get you to object. Minor objections will label you as a whiner.

·  What is more important to you: the money or the work? - Money is always important, but the work is the most important. There is no better answer.

·  What would your previous supervisor say your strongest point is? - There are numerous good possibilities: Loyalty, Energy, Positive attitude, Leadership, Team player, Expertise, Initiative, Patience, Hard work, Creativity, Problem solver

·  Tell me about a problem you had with a supervisor - Biggest trap of all. This is a test to see if you will speak ill of your boss. If you fall for it and tell about a problem with a former boss, you may well below the interview right there. Stay positive and develop a poor memory about any trouble with a supervisor.

·  What has disappointed you about a job? - Don’t get trivial or negative. Safe areas are few but can include: Not enough of a challenge. You were laid off in a reduction Company did not win a contract, which would have given you more responsibility.

·  Tell me about your ability to work under pressure. - You may say that you thrive under certain types of pressure. Give an example that relates to the type of position applied for.

·  Do your skills match this job or another job more closely? - Probably this one. Do not give fuel to the suspicion that you may want another job more than this one.

·  What motivates you to do your best on the job? - This is a personal trait that only you can say, but good examples are: Challenge, Achievement, Recognition

·  Are you willing to work overtime? Nights? Weekends? - This is up to you. Be totally honest.

·  How would you know you were successful on this job? - Several ways are good measures: You set high standards for yourself and meet them. Your outcomes are a success.Your boss tell you that you are successful

·  Would you be willing to relocate if required? - You should be clear on this with your family prior to the interview if you think there is a chance it may come up. Do not say yes just to get the job if the real answer is no. This can create a lot of problems later on in your career. Be honest at this point and save yourself future grief.

·  Are you willing to put the interests of the organization ahead of your own? - This is a straight loyalty and dedication question. Do not worry about the deep ethical and philosophical implications. Just say yes.

·  Describe your management style. - Try to avoid labels. Some of the more common labels, like progressive, salesman or consensus, can have several meanings or descriptions depending on which management expert you listen to. The situational style is safe, because it says you will manage according to the situation, instead of one size fits all.

·  What have you learned from mistakes on the job? - Here you have to come up with something or you strain credibility. Make it small, well intentioned mistake with a positive lesson learned. An example would be working too far ahead of colleagues on a project and thus throwing coordination off.

·  Do you have any blind spots? - Trick question. If you know about blind spots, they are no longer blind spots. Do not reveal any personal areas of concern here. Let them do their own discovery on your bad points. Do not hand it to them.

·  If you were hiring a person for this job, what would you look for? - Be careful to mention traits that are needed and that you have.

·  Do you think you are overqualified for this position? - Regardless of your qualifications, state that you are very well qualified for the position.

·  How do you propose to compensate for your lack of experience? - First, if you have experience that the interviewer does not know about, bring that up: Then, point out (if true) that you are a hard working quick learner.

·  What qualities do you look for in a boss? - Be generic and positive. Safe qualities are knowledgeable, a sense of humor, fair, loyal to subordinates and holder of high standards. All bosses think they have these traits.

·  Tell me about a time when you helped resolve a dispute between others. - Pick a specific incident. Concentrate on your problem solving technique and not the dispute you settled.

·  What position do you prefer on a team working on a project? - Be honest. If you are comfortable in different roles, point that out.

·  Describe your work ethic. - Emphasize benefits to the organization. Things like, determination to get the job done and work hard but enjoy your work are good.

·  What has been your biggest professional disappointment? - Be sure that you refer to something that was beyond your control. Show acceptance and no negative feelings.

·  Tell me about the most fun you have had on the job. - Talk about having fun by accomplishing something for the organization.

·  Do you have any questions for me? - Always have some questions prepared. Questions prepared where you will be an asset to the organization are good. How soon will I be able to be productive? and What type of projects will I be able to assist on? are examples

SQL Server DBA Interview Questions 6

Microsoft Sql Server 2005 Interview Questions and Answers

1.    What does integration of .NET Framework mean for SQL Server 2005?
This feature enables us to execute C# or VB.NET code in the DBMS to take advantage of the .NET functionality. This feature gives more flexibility in writing complex stored procedures, functions, and triggers that can be written in .net compatible language.
2.    What is SSIS?
According to Microsoft SQL Server Integration Services, “(SSIS) is an effective set of tools for both the traditional demands of ETL operations, as well as for the evolving needs of general purpose data integration.” In short, it is the next version of DTS (Data Transformation Services). ETL stands for Extract, Transform and Loading. In short it is a data migration tool that is flexible, fast, and has scalable architecture that enables effective data integration in current business environments.
3.    What is MARS?
In previous versions of SQL Server, applications had to process or cancel all result sets from one batch before it could execute any other batch on that connection. SQL Server 2005 introduces a new connection attribute that allows applications to have more than one pending request per connection, and in particular, to have more than one active default result set per connection. Multiple Active Result Sets (MARS) is the ability to have more than one pending request under a given SQL Server connection. MARS is a programming model enhancement that allows multiple requests to interleave in the server. We need to note that it is not a parallel execution in the server. However, it may benefit us with some performance benefits if used correctly. By default, this feature is not set in SQL Server 2005.
4.    What are the Security Enhancements in SQL Server 2005?
SQL Server 2005 enables administrators to manage permissions at a granular level.
·         In the new SQL Server 2005, we can specify a context under which statements in a module can execute.
·         SQL Server 2005 clustering supports Kerberos authentication against a SQL Server 2005 virtual server.
·         Administrators can specify Microsoft Windows-style policies on standard logins so that a consistent policy is applied across all accounts in the domain.
·         SQL Server 2005 supports encryption capabilities within the database itself, fully integrated with a key management infrastructure. By default, client-server communications are encrypted.
5.    What is new with the Reporting services in SQL server 2005?
SQL Server 2005 Reporting Services is a key component of SQL Server 2005 that provides customers with an enterprise-capable reporting platform. This comprehensive environment is used for authoring, managing, and delivering reports to the entire organization. SQL Server 2005 reporting services have some major changes when compared with the previous version.
·         Changes to the core functionality of the Reporting services in the design of the report, processing, and interactivity
·         Better Integration with other components – Enhanced integration with other components within SQL Server 2005 like SSIS, SSAS and SQL Server Management studio
·         Report Builder – A new reporting tool that enables business users to create their own reports
6.    What is OLAP?
Online Analytical Processing (OLAP) allows us to access aggregated and organized data from business data sources, such as data warehouses, in a multidimensional structure called a cube. The arrangement of data into cubes avoids a limitation of relational databases which are not well suited for near instantaneous analysis of large amounts of data. OLAP cubes can be thought of as extensions to the two-dimensional array of a spreadsheet.
7.    What is Data Mining?
According to MSDN Data, mining is “the process of extracting valid, authentic, and actionable information from large databases.” Microsoft data mining tools are different from traditional data mining applications in significant ways. Data Mining is a platform for developing intelligent applications, not a stand-alone application. You can build custom applications that are intelligent because the data mining models are easily accessible to the outside world. Further, the model is extensible so that third parties can add custom algorithms to support particular mining needs.
8.    What is new with the Analysis Services (SSAS) in SQL Server 2005?
SQL Server 2005 Analysis Services (SSAS) delivers online analytical processing (OLAP) and data mining functionality through a combination of server and client technologies, further reinforced through the use of a specialized development and management environment coupled with a well-defined object model for designing, creating, deploying, and maintaining business intelligence applications. The server component of Analysis Services is implemented as a Microsoft Windows service. Clients communicate with Analysis Services using the public standard XML for Analysis (XMLA), a SOAP-based protocol. Let us see the enhancements of made to SSAS.
·         Supports up to 16 instances of Analysis Services Service.
·         As discussed above, the Analysis Services service fully implements the XML for Analysis (XMLA) 1.1 specification. All communication with an instance of Analysis Services is handled through XMLA commands in SOAP messages.
·         Uses the Proactive caching.
9.    What is Information Schema in SQL Sever 2005?
Information Schema is the part of the SQL- 92 standard which exposes the metadata of the database. In SQL server, a set of views are created in each of the databases which exposes the metadata of the database. The information schema is kept in a separate schema – information schema – which exists in all databases, but which is not included in the search path by default. For more information regarding Information schema please read this article.
10. What is Full Text Search? How does it get implemented in SQL server 2005?
Full-text search allows fast and flexible indexing for keyword-based query of text data stored in a Microsoft SQL Server database. In contrast to the LIKE predicate which only works on character patterns, full-text queries perform linguistic searches against this data, by operating on words and phrases based on rules of a particular language.
11. What is integration of Microsoft Office System mean?
The integration with Microsoft Office system means the following.
·         Table Analysis Tools for Excel: Provides an easy-to-use add-in that leverages SQL Server 2005 Data Mining behind the scenes to perform powerful end user analysis on spreadsheet data.
·         Data Mining Client for Excel: Offers a full data mining model development lifecycle directly within Excel 2007.
·         Data Mining Templates for Visio: Enables powerful rendering and sharing of mining models as annotatable Visio 2007 drawings.
12. What is the support of Web Services in SQL Server 2005?
With this feature the database engine can be directly exposed as a web service without a middle tier or even an IIS. This will enable the user to directly call a stored procedure by calling a web method. This feature is designed with well-known standards such as SOAP 1.2, WSDL 1.1, and HTTP. With this new feature we can now connect to SQL Server not only with TDS- Tabular data stream (a binary protocol for connecting to SQL Server 2005) but also over SOAP/ HTTP.
13. What is OLTP?
Online Transaction Processing (OLTP) relational databases are optimal for managing changing data. When several users are performing transactions at the same time, OLTP databases are designed to let transactional applications write only the data needed to handle a single transaction as quickly as possible.
14. What is Snapshot in SQL Server 2005?
A database snapshot is a read-only, static view of a database, the source database. Each database snapshot is transaction-consistent with the source database as it existed at the time of the snapshot’s creation.
15. What is snapshot isolation in SQL Server 2005?
SQL Server 2005 introduces a new “snapshot” isolation level that is intended to enhance concurrency for online transaction processing (OLTP) applications. In prior versions of SQL Server, concurrency was based solely on locking, which can cause blocking and deadlocking problems for some applications. Snapshot isolation depends on enhancements to row versioning and is intended to improve performance by avoiding reader-writer blocking scenarios.
16. What is Database Partitioning in SQL Server 2005?
SQL Server 2005 provides a new capability for the partitioning of tables across file groups in a database. Partitioning a database improves performance and simplifies maintenance. By splitting a large table into smaller, individual tables, queries accessing only a fraction of the data can run faster because there is less data to scan.
17. What is SQL Server Agent?
SQL Server Agent is a Microsoft Windows service that executes scheduled administrative tasks called jobs. SQL Server Agent uses SQL Server to store job information. Jobs contain one or more job steps. We generally schedule the backups on the production databases using the SQL server agent. In SQL Server 2005 we have roles created for using SQL Server agents.
·         SQLAgentUserRole
·         SQLAgentReaderRole
·         SQLAgentOperatorRole
SQL Server Agent for SQL Server 2005 provides a more robust security design than earlier versions of SQL Server. This improved design gives system administrators the flexibility they need to manage their Agent service.
18. What is Replication? What is the need to have the replication? What are the enhancements made to SQL Server 2005 related to the replication?
“Replication is a set of technologies for copying and distributing data and database objects from one database to another and then synchronizing between databases to maintain consistency.” In short, replication is all about having multiple copies of the same database. We need replication when we need to distribute data to and from different locations. Generally we have a master copy of data. There will be multiple slaves (Clients) located at various locations which need to be replicated. We use replication for a variety of reasons. Load balancing is sharing the data among a number of servers and distributing the query load. Offline processing is one of the main reasons. In this scenario we need to modify the data on the database that is not connected to the network. The last reason may be to have a back-up to the database in case of failure to the existing database. Let us see the enhancements of SQL server 2005 database related to replication.
·         Database Mirroring – Database Mirroring is moving the transactions of database from one SQL Server database to another SQL server database on a different SQL Server.
·         Replication Management topology (RMO) – RMO is a new construct in SQL Server 2005. It is a .NET Framework library that provides a set of common language runtime classes for configuring, managing, and scripting replication, and for synchronizing Subscribers.
19. What are Business Logic Handlers?
Business logic handlers are written in managed code and allow us to execute custom business logic during the merge synchronization. We can invoke the business logic handler in case of non-conflicting data changes. Business logic handler can perform one of the following three actions.
·         Reject Data
·         Accept Data
·         Apply Custom Data
20. What are different variants of SQL Server 2005?
There are different variants of SQL Server 2005 commercially available.
·         Express – Free and only for one user
·         Enterprise – 5 users apart from server
·         Workgroup – 10 users apart from server
·         Standard – 25 users apart from server
21. What are Various Service packs available for SQL Server 2005?
As of now there are two service packs available for the SQL Server 2005.
·         Service Pack 1 – Has major changes or enhancements to SQL Server 2005 in Analysis Services, Data Programmability, SSIS, and reporting services.
·         Service Pack 2 – Unlike Service Pack 2, this service pack enables SQL Server 2005 customers to take advantage of the enhancements within Windows Vista and the 2007 Office system.

22. What are the New Data types introduced in SQL Server 2005?
SQL Server 2005 has added some new data types to its existing data types.
XML Data type
·         VARCHAR (MAX)
·         NVARCHAR (MAX)
·         VARBINARY (MAX)
As we can see, the new term MAX has been introduced in SQL Server 2005. This new specifier expands the storage capabilities of the varchar, nvarchar, and varbinary data types. Varchar(max), nvarchar(max), and varbinary(max) are collectively called large-value data types.
23. Does SQL Server 2005 support SMTP?
SQL Server 2005 now supports sending E-mail from the database. It is called as database mail and it uses DatabaseMail90.exe. Gone are the days when we were using a third party component for this. Receiving an e-mail was not supported in the previous versions of SQL Server.
24. What is SQL Management Object is SQL Server 2005?
These are collection of objects that are made for programming all aspects of managing Microsoft SQL Server 2005. SMO is a .NET based object model. It comes with SQL Server 2005 as a .Net assembly named Microsoft.SqlServer.Smo.dll. We can use these objects for connecting to a database, calling methods of the database that returns a table, using transactions, transferring data, scheduling administrative tasks, etc. The best part about SMO is that most of it can also be used with SQL server 2000.
25. What is SQL Service Broker in SQL Server 2005?
SQL Service broker is a new technology introduced in SQL Server 2005 for building database-intensive distributed applications. Basically, service broker has been built for developing applications that consist of individual components which are loosely coupled. Service broker supports asynchronous yet reliable messages that are passed between the components. These messages are called conversations.

Here are some SQL Server DBA/Developer interview questions I faced myself personally and/or heard from people. I will try to answer these questions briefly here, but be advised that these answers may not be complete and it will be better for you to go through text books, books online and other resources on the net.

Before you go for the interview, be prepared to explain the database design of one of your latest projects. Don't be surprised if the interviewer asks you to draw ER diagrams.

Well, here are some questions for you. Hope this helps you prepare for your interview. Wish you all the best in your job hunt! Feel free to email me 'interview questions' that you've faced.

Questions are categorized under the following sections, for your convenience:

What is normalization? Explain different levels of normalization?

Check out the article Q100139 from Microsoft knowledge base and of course, there's much more information available in the net. It'll be a good idea to get a hold of any RDBMS fundamentals text book, especially the one by C. J. Date. Most of the times, it will be okay if you can explain till third normal form.
What is denormalization and when would you go for it?
As the name indicates, denormalization is the reverse process of normalization. It's the controlled introduction of redundancy in to the database design. It helps improve the query performance as the number of joins could be reduced.
How do you implement one-to-one, one-to-many and many-to-many relationships while designing tables?
One-to-One relationship can be implemented as a single table and rarely as two tables with primary and foreign key relationships.
One-to-Many relationships are implemented by splitting the data into two tables with primary key and foreign key relationships.
Many-to-Many relationships are implemented using a junction table with the keys from both the tables forming the composite primary key of the junction table.

It will be a good idea to read up a database designing fundamentals text book.
What's the difference between a primary key and a unique key?
Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only.
What are user defined datatypes and when you should go for them?
User defined datatypes let you extend the base SQL Server datatypes by providing a descriptive name, and format to the database. Take for example, in your database, there is a column called Flight_Num which appears in many tables. In all these tables it should be varchar(8). In this case you could create a user defined datatype called Flight_num_type of varchar(8) and use it across all your tables.

See sp_addtype, sp_droptype in books online.
What is bit datatype and what's the information that can be stored inside a bit column?
Bit datatype is used to store boolean information like 1 or 0 (true or false). Untill SQL Server 6.5 bit datatype could hold either a 1 or 0 and there was no support for NULL. But from SQL Server 7.0 onwards, bit datatype can represent a third state, which is NULL. 
Define candidate key, alternate key, composite key.
A candidate key is one that can identify each row of a table uniquely. Generally a candidate key becomes the primary key of the table. If the table has more than one candidate key, one of them will become the primary key, and the rest are called alternate keys.

A key formed by combining at least two or more columns is called composite key. 
What are defaults? Is there a column to which a default can't be bound?
A default is a value that will be used by a column, if no value is supplied to that column while inserting data. IDENTITY columns and timestamp columns can't have defaults bound to them. See CREATE DEFUALT in books online.
What is a transaction and what are ACID properties?
A transaction is a logical unit of work in which, all the steps must be performed or none. ACID stands for Atomicity, Consistency, Isolation, Durability. These are the properties of a transaction. For more information and explanation of these properties, see SQL Server books online or any RDBMS fundamentals text book.
Explain different isolation levels
An isolation level determines the degree of isolation of data between concurrent transactions. The default SQL Server isolation level is Read Committed. Here are the other isolation levels (in the ascending order of isolation): Read Uncommitted, Read Committed, Repeatable Read, Serializable. See SQL Server books online for an explanation of the isolation levels. Be sure to read about SET TRANSACTION ISOLATION LEVEL, which lets you customize the isolation level at the connection level.
CREATE INDEX myIndex ON myTable(myColumn)

What type of Index will get created after executing the above statement?
Non-clustered index. Important thing to note: By default a clustered index gets created on the primary key, unless specified otherwise.
What's the maximum size of a row?
8060 bytes. Don't be surprised with questions like 'what is the maximum number of columns per table'. Check out SQL Server books online for the page titled: "Maximum Capacity Specifications".
Explain Active/Active and Active/Passive cluster configurations
Hopefully you have experience setting up cluster servers. But if you don't, at least be familiar with the way clustering works and the two clusterning configurations Active/Active and Active/Passive. SQL Server books online has enough information on this topic and there is a good white paper available on Microsoft site.
Explain the architecture of SQL Server
This is a very important question and you better be able to answer it if consider yourself a DBA. SQL Server books online is the best place to read about SQL Server architecture. Read up the chapter dedicated to SQL Server Architecture.
What is lock escalation?
Lock escalation is the process of converting a lot of low level locks (like row locks, page locks) into higher level locks (like table locks). Every lock is a memory structure too many locks would mean, more memory being occupied by locks. To prevent this from happening, SQL Server escalates the many fine-grain locks to fewer coarse-grain locks. Lock escalation threshold was definable in SQL Server 6.5, but from SQL Server 7.0 onwards it's dynamically managed by SQL Server.
What's the difference between DELETE TABLE and TRUNCATE TABLE commands?
DELETE TABLE is a logged operation, so the deletion of each row gets logged in the transaction log, which makes it slow. TRUNCATE TABLE also deletes all the rows in a table, but it won't log the deletion of each row, instead it logs the deallocation of the data pages of the table, which makes it faster. Of course, TRUNCATE TABLE can be rolled back.

Explain the storage models of OLAP
Check out MOLAP, ROLAP and HOLAP in SQL Server books online for more infomation.
What are the new features introduced in SQL Server 2000 (or the latest release of SQL Server at the time of your interview)? What changed between the previous version of SQL Server and the current version?
This question is generally asked to see how current is your knowledge. Generally there is a section in the beginning of the books online titled "What's New", which has all such information. Of course, reading just that is not enough, you should have tried those things to better answer the questions. Also check out the section titled "Backward Compatibility" in books online which talks about the changes that have taken place in the new version.
What are constraints? Explain different types of constraints.
Constraints enable the RDBMS enforce the integrity of the database automatically, without needing you to create triggers, rule or defaults.

Types of constraints: NOT NULL, CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY

For an explanation of these constraints see books online for the pages titled: "Constraints" and "CREATE TABLE", "ALTER TABLE"
Whar is an index? What are the types of indexes? How many clustered indexes can be created on a table? I create a separate index on each column of a table. what are the advantages and disadvantages of this approach?
Indexes in SQL Server are similar to the indexes in books. They help SQL Server retrieve the data quicker.

Indexes are of two types. Clustered indexes and non-clustered indexes. When you craete a clustered index on a table, all the rows in the table are stored in the order of the clustered index key. So, there can be only one clustered index per table. Non-clustered indexes have their own storage separate from the table data storage. Non-clustered indexes are stored as B-tree structures (so do clustered indexes), with the leaf level nodes having the index key and it's row locater. The row located could be the RID or the Clustered index key, depending up on the absence or presence of clustered index on the table.

If you create an index on each column of a table, it improves the query performance, as the query optimizer can choose from all the existing indexes to come up with an efficient execution plan. At the same t ime, data modification operations (such as INSERT, UPDATE, DELETE) will become slow, as every time data changes in the table, all the indexes need to be updated. Another disadvantage is that, indexes need disk space, the more indexes you have, more disk space is used.
What is RAID and what are different types of RAID configurations?

RAID stands for Redundant Array of Inexpensive Disks, used to provide fault tolerance to database servers. There are six RAID levels 0 through 5 offering different levels of performance, fault tolerance. MSDN has some information about RAID levels and for detailed information, check out the RAID advisory board's homepage
What are the steps you will take to improve performance of a poor performing query?
This is a very open ended question and there could be a lot of reasons behind the poor performance of a query. But some general issues that you could talk about would be: No indexes, table scans, missing or out of date statistics, blocking, excess recompilations of stored procedures, procedures and triggers without SET NOCOUNT ON, poorly written query with unnecessarily complicated joins, too much normalization, excess usage of cursors and temporary tables.

Some of the tools/ways that help you troubleshooting performance problems are: SET SHOWPLAN_ALL ON, SET SHOWPLAN_TEXT ON, SET STATISTICS IO ON, SQL Server Profiler, Windows NT /2000 Performance monitor, Graphical execution plan in Query Analyzer.

Download the white paper on performance tuning SQL Server from Microsoft web site. Don't forget to check out sql-server-performance.com
What are the steps you will take, if you are tasked with securing an SQL Server?
Again this is another open ended question. Here are some things you could talk about: Preferring NT authentication, using server, databse and application roles to control access to the data, securing the physical database files using NTFS permissions, using an unguessable SA password, restricting physical access to the SQL Server, renaming the Administrator account on the SQL Server computer, disabling the Guest account, enabling auditing, using multiprotocol encryption, setting up SSL, setting up firewalls, isolating SQL Server from the web server etc.

Read the white paper on SQL Server security from Microsoft website. Also check out My SQL Server security best practices


What is a deadlock and what is a live lock? How will you go about resolving deadlocks?
Deadlock is a situation when two processes, each having a lock on one piece of data, attempt to acquire a lock on the other's piece. Each process  would wait indefinitely for the other to release the lock, unless one of the user processes is terminated. SQL Server detects deadlocks and terminates one user's process.

A livelock is one, where a  request for an exclusive lock is repeatedly denied because a series of overlapping shared locks keeps interfering. SQL Server detects the situation after four denials and refuses further shared locks. A livelock also occurs when read transactions monopolize a table or page, forcing a write transaction to wait indefinitely.

Check out SET DEADLOCK_PRIORITY and "Minimizing Deadlocks"  in SQL Server books online. Also check out the article Q169960 from Microsoft knowledge base.
What is blocking and how would you troubleshoot it?
Blocking happens when one connection from an application holds a lock and a second connection requires a conflicting lock type. This forces the second connection to wait, blocked on the first.

Read up the following topics in SQL Server books online: Understanding and avoiding blocking, Coding efficient transactions.
Explain CREATE DATABASE syntax
Many of us are used to craeting databases from the Enterprise Manager or by just issuing the command: CREATE DATABAE MyDB. But what if you have to create a database with two filegroups, one on drive C and the other on drive D with log on drive E with an initial size of 600 MB and with a growth factor of 15%? That's why being a DBA you should be familiar with the CREATE DATABASE syntax. Check out SQL Server books online for more information.
How to restart SQL Server in single user mode? How to start SQL Server in minimal configuration mode?
SQL Server can be started from command line, using the SQLSERVR.EXE. This EXE has some very important parameters with which a DBA should be familiar with. -m is used for starting SQL Server in single user mode and -f is used to start the SQL Server in minimal confuguration mode. Check out SQL Server books online for more parameters and their explanations.
As a part of your job, what are the DBCC commands that you commonly use for database maintenance?
DBCC CHECKDB, DBCC CHECKTABLE, DBCC CHECKCATALOG, DBCC CHECKALLOC, DBCC SHOWCONTIG, DBCC SHRINKDATABASE, DBCC SHRINKFILE etc. But there are a whole load of DBCC commands which are very useful for DBAs. Check out SQL Server books online for more information.
What are statistics, under what circumstances they go out of date, how do you update them?
Statistics determine the selectivity of the indexes. If an indexed column has unique values then the selectivity of that index is more, as opposed to an index with non-unique values. Query optimizer uses these indexes in determining whether to choose an index or not while executing a query.

Some situations under which you should update statistics:
1) If there is significant change in the key values in the index
2) If a large amount of data in an indexed column has been added, changed, or removed (that is, if the distribution of key values has changed), or the table has been truncated using the TRUNCATE TABLE statement and then repopulated
3) Database is upgraded from a previous version

Look up SQL Server books online for the following commands: UPDATE STATISTICS, STATS_DATE, DBCC SHOW_STATISTICS, CREATE STATISTICS, DROP STATISTICS, sp_autostats, sp_createstats, sp_updatestats
What are the different ways of moving data/databases between servers and databases in SQL Server?
There are lots of options available, you have to choose your option depending upon your requirements. Some of the options you have are: BACKUP/RESTORE, dettaching and attaching databases, replication, DTS, BCP, logshipping, INSERT...SELECT, SELECT...INTO, creating INSERT scripts to generate data.
Explian different types of BACKUPs avaialabe in SQL Server? Given a particular scenario, how would you go about choosing a backup plan?
Types of backups you can create in SQL Sever 7.0+ are Full database backup, differential database backup, transaction log backup, filegroup backup. Check out the BACKUP and RESTORE commands in SQL Server books online. Be prepared to write the commands in your interview. Books online also has information on detailed backup/restore architecture and when one should go for a particular kind of backup.
What is database replicaion? What are the different types of replication you can set up in SQL Server?
Replication is the process of copying/moving data between databases on the same or different servers. SQL Server supports the following types of replication scenarios:

• Snapshot replication
• Transactional replication (with immediate updating subscribers, with queued updating subscribers)
• Merge replication

See SQL Server books online for indepth coverage on replication. Be prepared to explain how different replication agents function, what are the main system tables used in replication etc.
How to determine the service pack currently installed on SQL Server?
The global variable @@Version stores the build number of the sqlservr.exe, which is used to determine the service pack installed. To know more about this process visit SQL Server service packs and versions.
What are cursors? Explain different types of cursors. What are the disadvantages of cursors? How can you avoid cursors?

Cursors allow row-by-row prcessing of the resultsets.

Types of cursors: Static, Dynamic, Forward-only, Keyset-driven. See books online for more information.

Disadvantages of cursors: Each time you fetch a row from the cursor, it results in a network roundtrip, where as a normal SELECT query makes only one rowundtrip, however large the resultset is. Cursors are also costly because they require more resources and temporary storage (results in more IO operations). Furthere, there are restrictions on the SELECT statements that can be used with some types of cursors.

Most of the times, set based operations can be used instead of cursors. Here is an example:

If you have to give a flat hike to your employees using the following criteria:

Salary between 30000 and 40000 -- 5000 hike
Salary between 40000 and 55000 -- 7000 hike
Salary between 55000 and 65000 -- 9000 hike

In this situation many developers tend to use a cursor, determine each employee's salary and update his salary according to the above formula. But the same can be achieved by multiple update statements or can be combined in a single UPDATE statement as shown below:

UPDATE tbl_emp SET salary =
CASE WHEN salary BETWEEN 30000 AND 40000 THEN salary + 5000
WHEN salary BETWEEN 40000 AND 55000 THEN salary + 7000
WHEN salary BETWEEN 55000 AND 65000 THEN salary + 10000
END

Another situation in which developers tend to use cursors: You need to call a stored procedure when a column in a particular row meets certain condition. You don't have to use cursors for this. This can be achieved using WHILE loop, as long as there is a unique key to identify each row. For examples of using WHILE loop for row by row processing, check out the 'My code library' section of my site or search for WHILE.
Write down the general syntax for a SELECT statements covering all the options.
Here's the basic syntax: (Also checkout SELECT in books online for advanced syntax).

SELECT select_list
[INTO new_table_]
FROM table_source
[WHERE search_condition]
[GROUP BY group_by_expression]
[HAVING search_condition]
[ORDER BY order_expression [ASC | DESC] ]

What is a join and explain different types of joins.
Joins are used in queries to explain how different tables are related. Joins also let you select data from a table depending upon data from another table.

Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS.

For more information see pages from books online titled: "Join Fundamentals" and "Using Joins".
Can you have a nested transaction?
Yes, very much. Check out BEGIN TRAN, COMMIT, ROLLBACK, SAVE TRAN and @@TRANCOUNT
What is an extended stored procedure? Can you instantiate a COM object by using T-SQL?
An extended stored procedure is a function within a DLL (written in a programming language like C, C++ using Open Data Services (ODS) API) that can be called from T-SQL, just the way we call normal stored procedures using the EXEC statement. See books online to learn how to create extended stored procedures and how to add them to SQL Server.

Yes, you can instantiate a COM (written in languages like VB, VC++) object from T-SQL by using sp_OACreate stored procedure. Also see books online for sp_OAMethod, sp_OAGetProperty, sp_OASetProperty, sp_OADestroy. For an example of creating a COM object in VB and calling it from T-SQL, see 'My code library' section of this site.
What is the system function to get the current user's user id?
USER_ID(). Also check out other system functions like USER_NAME(), SYSTEM_USER, SESSION_USER, CURRENT_USER, USER, SUSER_SID(), HOST_NAME().
What are triggers? How many triggers you can have on a table? How to invoke a trigger on demand?
Triggers are special kind of stored procedures that get executed automatically when an INSERT, UPDATE or DELETE operation takes place on a table.

In SQL Server 6.5 you could define only 3 triggers per table, one for INSERT, one for UPDATE and one for DELETE. From SQL Server 7.0 onwards, this restriction is gone, and you could create multiple triggers per each action. But in 7.0 there's no way to control the order in which the triggers fire. In SQL Server 2000 you could specify which trigger fires first or fires last using sp_settriggerorder

Triggers can't be invoked on demand. They get triggered only when an associated action (INSERT, UPDATE, DELETE) happens on the table on which they are defined.

Triggers are generally used to implement business rules, auditing. Triggers can also be used to extend the referential integrity checks, but wherever possible, use constraints for this purpose, instead of triggers, as constraints are much faster.

Till SQL Server 7.0, triggers fire only after the data modification operation happens. So in a way, they are called post triggers. But in SQL Server 2000 you could create pre triggers also. Search SQL Server 2000 books online for INSTEAD OF triggers.

Also check out books online for 'inserted table', 'deleted table' and COLUMNS_UPDATED()

There is a trigger defined for INSERT operations on a table, in an OLTP system. The trigger is written to instantiate a COM object and pass the newly insterted rows to it for some custom processing. What do you think of this implementation? Can this be implemented better?
Instantiating COM objects is a time consuming process and since you are doing it from within a trigger, it slows down the data insertion process. Same is the case with sending emails from triggers. This scenario can be better implemented by logging all the necessary data into a separate table, and have a job which periodically checks this table and does the needful.
What is a self join? Explain it with an example.
Self join is just like any other join, except that two instances of the same table will be joined in the query. Here is an example: Employees table which contains rows for normal employees as well as managers. So, to find out the managers of all the employees, you need a self join.

CREATE TABLE emp
(
empid int,
mgrid int,
empname char(10)
)

INSERT emp SELECT 1,2,'Vyas'
INSERT emp SELECT 2,3,'Mohan'
INSERT emp SELECT 3,NULL,'Shobha'
INSERT emp SELECT 4,2,'Shridhar'
INSERT emp SELECT 5,2,'Sourabh'

SELECT t1.empname [Employee], t2.empname [Manager]
FROM emp t1, emp t2
WHERE t1.mgrid = t2.empid

Here's an advanced query using a LEFT OUTER JOIN that even returns the employees without managers (super bosses)

SELECT t1.empname [Employee], COALESCE(t2.empname, 'No manager') [Manager]
FROM emp t1
LEFT OUTER JOIN
emp t2
ON
t1.mgrid = t2.empid