SQL Server Interview Questions & Answers

What is MySQL

MySQL is a fast, easy to use relational database. It is currently the most popular open-source database. It is very commonly used in conjunction with PHP scripts to create powerful and dynamic server-side applications.

MySQL is used for many small and big businesses. It is developed, marketed and supported by MySQL AB, a Swedish company. It is written in C and C++,If you are intrested to learn about SQL Server please visit SQl Server DBA online training Hyderabad

1. What are the two authentication modes in SQL Server?

There are two authentication modes –

• Windows Mode
• Mixed Mode  

Modes can be changed by selecting the tools menu of SQL Server configuration properties and choose security page.

2. What Is SQL Profiler?

SQL Profiler is a tool which allows system administrator to monitor events in the SQL server. This is mainly used to capture and save data about each event of a file or a table for analysis.

3. What is recursive stored procedure?

SQL Server supports recursive stored procedure which calls by itself. Recursive stored procedure can be defined as a method of problem solving wherein the solution is arrived repetitively. It can nest up to 32 levels.

CREATE PROCEDURE [dbo].[Fact]
(
@Number Integer,
@RetVal Integer OUTPUT
)
AS
DECLARE @In Integer
DECLARE @Out Integer
IF @Number != 1
BEGIN
SELECT @In = @Number – 1
EXEC Fact @In, @Out OUTPUT - Same stored procedure has been called again(Recursively)
SELECT @RetVal = @Number * @Out
END
ELSE
BEGIN
SELECT @RetVal = 1
END
RETURN
GO

4. What are the differences between local and global temporary tables?

• Local temporary tables are visible when there is a connection, and are deleted when the connection is closed.

CREATE TABLE #<tablename>

• Global temporary tables are visible to all users, and are deleted when the connection that created it is closed.

CREATE TABLE ##<tablename>

5. What is CHECK constraint?

A CHECK constraint can be applied to a column in a table to limit the values that can be placed in a column. Check constraint is to enforce integrity.

6. Can SQL servers linked to other servers?

SQL server can be connected to any database which has OLE-DB provider to give a link. Example: Oracle has OLE-DB provider which has link to connect with the SQL server group.

7. What is sub query and its properties?

A sub-query is a query which can be nested inside a main query like Select, Update, Insert or Delete statements. This can be used when expression is allowed. Properties of sub query can be defined as

• A sub query should not have order by clause
• A sub query should be placed in the right hand side of the comparison operator of the main query
• A sub query should be enclosed in parenthesis because it needs to be executed first before the main query
• More than one sub query can be included

8. What are the types of sub query?

There are three types of sub query –

• Single row sub query which returns only one row
• Multiple row sub query which returns multiple rows
• Multiple column sub query which returns multiple columns to the main query. With that sub query result, Main query will be executed.

9. What is SQL server agent?

The SQL Server agent plays a vital role in day to day tasks of SQL server administrator(DBA). Server agent's purpose is to implement the tasks easily with the scheduler engine which allows our jobs to run at scheduled date and time.

10. What are scheduled tasks in SQL Server?

Scheduled tasks or jobs are used to automate processes that can be run on a scheduled time at a regular interval. This scheduling of tasks helps to reduce human intervention during night time and feed can be done at a particular time. User can also order the tasks in which it has to be generated.

11. What is COALESCE in SQL Server?

COALESCE is used to return first non-null expression within the arguments. This function is used to return a non-null from more than one column in the arguments.

Example –

Select COALESCE(empno, empname, salary) from employee;

12. How exceptions can be handled in SQL Server Programming?

Exceptions are handled using TRY----CATCH constructs and it is handles by writing scripts inside the TRY block and error handling in the CATCH block.To Learn SQL programming please visit  SQl Server DBA online training

13. What is the purpose of FLOOR function?

FLOOR function is used to round up a non-integer value to the previous least integer. Example is given

FLOOR(6.7)

Returns 6.

14. Can we check locks in database? If so, how can we do this lock check?

Yes, we can check locks in the database. It can be achieved by using in-built stored procedure called sp_lock.

15. What is the use of SIGN function?

SIGN function is used to determine whether the number specified is Positive, Negative and Zero. This will return +1,-1 or 0.

Example –

SIGN(-35) returns -1

16. What is a Trigger?

Triggers are used to execute a batch of SQL code when insert or update or delete commands are executed against a table. Triggers are automatically triggered or executed when the data is modified. It can be executed automatically on insert, delete and update operations.

17. What are the types of Triggers?

There are four types of triggers and they are:

• Insert
• Delete
• Update
• Instead of

18. What is an IDENTITY column in insert statements?

IDENTITY column is used in table columns to make that column as Auto incremental number or a surrogate key.

19. What is Bulkcopy in SQL?

Bulkcopy is a tool used to copy large amount of data from Tables. This tool is used to load large amount of data in SQL Server.

20. What will be query used to get the list of triggers in a database?

Query to get the list of triggers in database-

Select * from sys.objects where type='tr'

21. What is the difference between UNION and UNION ALL?

• UNION: To select related information from two tables UNION command is used. It is similar to JOIN command.
• UNION All: The UNION ALL command is equal to the UNION command, except that UNION ALL selects all values. It will not remove duplicate rows, instead it will retrieve all rows from all tables.

22. How Global temporary tables are represented and its scope?

Global temporary tables are represented with ## before the table name. Scope will be the outside the session whereas local temporary tables are inside the session. Session ID can be found using @@SPID.

23. What are the differences between Stored Procedure and the dynamic SQL?

Stored Procedure is a set of statements which is stored in a compiled form. Dynamic SQL is a set of statements that dynamically constructed at runtime and it will not be stored in a Database and it simply execute during run time.

24. What is Collation?

Collation is defined to specify the sort order in a table. There are three types of sort order –

1. Case sensitive
2. Case Insensitive
3. Binary

25. How can we get count of the number of records in a table?

Following are the queries can be used to get the count of records in a table -

Select * from <tablename> Select count(*) from <tablename> Select rows from sysindexes where id=OBJECT_ID(tablename) and indid<2