Interview Questions for MS SQL Server (DBA)

Interview questions for MS SQL  Server

Interview Questions for MS SQL  Server (DBA)

 

This one always gets asked. For a
while the database interview questions were limited to Oracle and generic
database design questions. This is a set of more than a hundred Microsoft SQL
Server interview questions. Some questions are open-ended, and some do not
have answers.

1. What is normalization? – Well a relational database is basically composed of tables that contain related data. So the Process of organizing this data into tables is
   actually referred to as normalization.
2. What is a Stored Procedure? - Its nothing but a set of
   T-SQL statements combined to perform a single task of several tasks. Its
   basically like a Macro so when you invoke the Stored procedure, you
   actually run a set of statements.
3. Can you give an example of
   Stored Procedure? - sp_helpdb , sp_who2, sp_renamedb are a set of system
   defined stored procedures. We can also have user defined stored
   procedures which can be called in similar way.
4. What is a trigger? - Triggers
   are basically used to implement business rules. Triggers is also similar
   to stored procedures. The difference is that it can be activated when
   data is added or edited or deleted from a table in a database.
5. What is a view? - If we have
   several tables in a db and we want to view only specific columns from
   specific tables we can go for views. It would also suffice the needs of
   security some times allowing specfic users to see only specific columns
   based on the permission that we can configure on the view. Views also
   reduce the effort that is required for writing queries to access
   specific columns every time.
6. What is an Index? - When
   queries are run against a db, an index on that db basically helps in the
   way the data is sorted to process the query for faster and data
   retrievals are much faster when we have an index.
7. What are the types of indexes
   available with SQL Server? - There are basically two types of indexes
   that we use with the SQL Server. Clustered and the
   Non-Clustered.
8. What is the basic difference
   between clustered and a non-clustered
   index? - The difference is that,
   Clustered index is unique for any given table and we can have only one
   clustered index on a table. The leaf level of a clustered index is the
   actual data and the data is resorted in case of clustered index. Whereas
   in case of non-clustered index the leaf level is actually a pointer to
   the data in rows so we can have as many non-clustered indexes as we can
   on the db.
9. What are cursors? - Well cursors
   help us to do an operation on a set of data that we retreive by commands
   such as Select columns from table. For example : If we have duplicate
   records in a table we can remove it by declaring a cursor which would
   check the records during retreival one by one and remove rows which have
   duplicate values.
10. When do we use the
    UPDATE_STATISTICS command? - This command is basically used when we do a
    large processing of data. If we do a large amount of deletions any
    modification or Bulk Copy into the tables, we need to basically update
    the indexes to take these changes into account. UPDATE_STATISTICS
    updates the indexes on these tables accordingly.
11. Which TCP/IP port does SQL
    Server run on? - SQL Server runs on port 1433 but we can also change it
    for better security.
12. From where can you change the
    default port? - From the Network Utility TCP/IP properties –> Port
    number.both on client and the server.
13. Can you tell me the
    difference between DELETE & TRUNCATE commands? - Delete command
    removes the rows from a table based on the condition that we provide
    with a WHERE clause. Truncate will actually remove all the rows from a
    table and there will be no data in the table after we run the truncate
    command.
14. Can we use Truncate command
    on a table which is referenced by FOREIGN KEY? - No. We cannot use
    Truncate command on a table with Foreign Key because of referential
    integrity.
15. What is the use of DBCC
    commands? - DBCC stands for database consistency checker. We use these
    commands to check the consistency of the databases, i.e., maintenance,
    validation task and status checks.
16. Can you give me some DBCC
    command options?(Database consistency check) - DBCC CHECKDB - Ensures
    that tables in the db and the indexes are correctly linked.and DBCC
    CHECKALLOC - To check that all pages in a db are correctly allocated.
    DBCC SQLPERF - It gives report on current usage of transaction log in
    percentage. DBCC CHECKFILEGROUP - Checks all tables file group for any
    damage.
17. What command do we use to
    rename a db? - sp_renamedb ‘oldname’ , ‘newname’
18. Well sometimes sp_reanmedb
    may not work you know because if some one is using the db it will not
    accept this command so what do you think you can do in such cases? - In
    such cases we can first bring to db to single user using sp_dboptions
    and then we can rename that db and then we can rerun the sp_dboptions
    command to remove the single user mode.
19. What is the difference
    between a HAVING CLAUSE and a WHERE CLAUSE? - Having Clause is basically
    used only with the GROUP BY function in a query. WHERE Clause is applied
    to each row before they are part of the GROUP BY function in a query.
20. What do you mean by
    COLLATION? - Collation is basically the sort order. There are three
    types of sort order Dictionary case sensitive, Dictonary - case
    insensitive and Binary.
21. What is a Join in SQL Server?
    - Join actually puts data from two or more tables into a single result
    set.
22. Can you explain the types of
    Joins that we can have with Sql Server? - There are three types of
    joins: Inner Join, Outer Join, Cross Join
23. When do you use SQL Profiler? - SQL Profiler utility
    allows us to basically track connections to the SQL Server and also
    determine activities such as which SQL Scripts are running, failed jobs
    etc..
24. What is a Linked Server? - Linked Servers is a
    concept in SQL Server by which we can add other SQL Server to a Group
    and query both the SQL Server dbs using T-SQL Statements.
25. Can you link only other SQL
    Servers or any database servers such as Oracle? - We can link any server
    provided we have the OLE-DB provider from Microsoft to allow a link. For
    Oracle we have a OLE-DB provider for oracle that microsoft provides to
    add it as a linked server to the sql server group.
26. Which stored procedure will
    you be running to add a linked server? - sp_addlinkedserver, sp_addlinkedsrvlogin
27. What are the OS services that
    the SQL Server installation adds? - MS SQL SERVER SERVICE, SQL AGENT
    SERVICE, DTC (Distribution transac co-ordinator)
28. Can you explain the role of
    each service? - SQL SERVER - is for running the databases SQL AGENT - is
    for automation such as Jobs, DB Maintanance, Backups DTC - Is for
    linking and connecting to other SQL Servers
29. How do you troubleshoot SQL
    Server if its running very slow? - First check the processor and memory
    usage to see that processor is not above 80% utilization and memory not
    above 40-45% utilization then check the disk utilization using
    Performance Monitor, Secondly, use SQL Profiler to check for the users
    and current SQL activities and jobs running which might be a problem.
    Third would be to run UPDATE_STATISTICS command to update the indexes
30. Lets say due to N/W or
    Security issues client is not able to connect to server or vice versa.
    How do you troubleshoot? - First I will look to ensure that port
    settings are proper on server and client Network utility for
    connections. ODBC is properly configured at client end for connection
    ——Makepipe & readpipe are utilities to check for connection.
    Makepipe is run on Server and readpipe on client to check for any
    connection issues.
31. What are the authentication
    modes in SQL Server? - Windows mode and mixed mode (SQL & Windows).
32. Where do you think the users
    names and passwords will be stored in sql server? - They get stored in
    master db in the sysxlogins table.
33. What is log shipping? Can we
    do logshipping with SQL Server 7.0 - Logshipping is a new feature of SQL
    Server 2000. We should have two SQL Server - Enterprise Editions. From
    Enterprise Manager we can configure the logshipping. In logshipping the
    transactional log file from one server is automatically updated into the
    backup database on the other server. If one server fails, the other
    server will have the same db and we can use this as the DR (disaster
    recovery) plan.
34. Let us say the SQL Server
    crashed and you are rebuilding the databases including the master
    database what procedure to you follow? - For restoring the master db we
    have to stop the SQL Server first and then from command line we can type
    SQLSERVER –m which will basically bring it into the maintenance mode
    after which we can restore the master db.
35. Let us say master db itself
    has no backup. Now you have to rebuild the db so what kind of action do
    you take? - (I am not sure- but I think we have a command to do it).
36. What is BCP? When do we use
    it? - BulkCopy is a tool used to copy huge amount of data from tables
    and views. But it won’t copy the structures of the same.
37. What should we do to copy the
    tables, schema and views from one SQL Server to another? - We have to
    write some DTS packages for it.
38. What are the different types
    of joins and what dies each do?
39. What are the four main query
    statements?
40. What is a sub-query? When
    would you use one?
41. What is a NOLOCK?
42. What are three SQL keywords
    used to change or set someone’s permissions?
43. What is the difference
    between HAVING clause and the WHERE clause?
44. What is referential
    integrity? What are the advantages of it?
45. What is database
    normalization?
46. Which command using Query
    Analyzer will give you the version of SQL server and operating system?
47. Using query analyzer, name 3
    ways you can get an accurate count of the number of records in a table?
48. What is the purpose of using
    COLLATE in a query?
49. What is a trigger?
50. What is one of the first
    things you would do to increase performance of a query? For example, a
    boss tells you that “a query that ran yesterday took 30 seconds, but
    today it takes 6 minutes”
51. What is an execution plan?
    When would you use it? How would you view the execution plan?
52. What is the STUFF function
    and how does it differ from the REPLACE function?
53. What does it mean to have
    quoted_identifier on? What are the implications of having it off?
54. What are the different types
    of replication? How are they used?
55. What is the difference
    between a local and a global variable?
56. What is the difference
    between a Local temporary table and a Global temporary table? How is
    each one used?
57. What are cursors? Name four
    types of cursors and when each one would be applied?
58. What is the purpose of UPDATE
    STATISTICS?
59. How do you use DBCC
    statements to monitor various aspects of a SQL server installation?
60. How do you load large data to
    the SQL server database?
61. How do you check the
    performance of a query and how do you optimize it?
62. How do SQL server 2000 and
    XML linked? Can XML be used to access data?
63. What is SQL server agent?
64. What is referential integrity
    and how is it achieved?
65. What is indexing?
66. What is normalization and
    what are the different forms of normalizations?
67. Difference between
    server.transfer and server.execute method?
68. What id de-normalization and
    when do you do it?
69. What is better - 2nd Normal
    form or 3rd normal form? Why?
70. Can we rewrite subqueries
    into simple select statements or with joins? Example?
71. What is a function? Give some
    example?
72. What is a stored procedure?
73. Difference between Function
    and Procedure-in general?
74. Difference between Function
    and Stored Procedure?
75. Can a stored procedure call
    another stored procedure. If yes what level and can it be controlled?
76. Can a stored procedure call
    itself(recursive). If yes what level and can it be controlled.?
77. How do you find the number of
    rows in a table?
78. Difference between Cluster
    and Non-cluster index?
79. What is a table called, if it
    does not have neither Cluster nor Non-cluster Index?
80. Explain DBMS, RDBMS?
81. Explain basic SQL queries
    with SELECT from where Order By, Group By-Having?
82. Explain the basic concepts of
    SQL server architecture?
83. Explain couple pf features of
    SQL server
84. Scalability, Availability,
    Integration with internet, etc.)?
85. Explain fundamentals of Data
    ware housing & OLAP?
86. Explain the new features of
    SQL server 2000?
87. How do we upgrade from SQL
    Server 6.5 to 7.0 and 7.0 to 2000?
88. What is data integrity?
    Explain constraints?
89. Explain some DBCC commands?
90. Explain sp_configure
    commands, set commands?
91. Explain what are db_options
    used for?
92. What is the basic functions
    for master, msdb, tempdb databases?
93. What is a job?
94. What are tasks?
95. What are primary keys and
    foreign keys?
96. How would you Update the rows
    which are divisible by 10, given a set of numbers in column?
97. If a stored procedure is
    taking a table data type, how it looks?
98. How m-m relationships are
    implemented?
99. How do you know which index a
    table is using?
100. How will oyu test the stored
     procedure taking two parameters namely first name and last name
     returning full name?
101. How do you find the error,
     how can you know the number of rows effected by last SQL statement?
102. How can you get @@error and
     @@rowcount at the same time?
103. What are sub-queries? Give
     example? In which case sub-queries are not feasible?
104. What are the type of joins?
     When do we use Outer and Self joins?
105. Which virtual table does a
     trigger use?
106. How do you measure the
     performance of a stored procedure?
107. Questions regarding Raiseerror?
     
     
108. Questions on identity?
109. If there is failure during
     updation of certain rows, what will be the state?