SQL Interview Questions and Answers
Looking out for SQL interview questions and answers to clear SQL Server interview with ease and confidence.
SQL Interview Questions – What is normalization?
– Well a database is largely composed of tables that contain connected data. that the method of organizing this information into tables is truly brought up as normalisation.
SQL Interview Questions – What is a keep Procedure?
– Its nothing however a collection of T-SQL statements combined to perform one task of many tasks. Its primarily sort of a Macro thus once you invoke the keep procedure, you really run a collection of statements.
SQL Interview Questions – Can you offer associate example of keep Procedure?
– sp_helpdb , sp_who2, sp_renamedb square measure a collection of system outlined keep procedures. we are able to even have user outlined keep procedures which may be referred to as in similar means.
What is a trigger?
– Triggers square measure primarily wont to implement business rules. Triggers is additionally like keep procedures. The distinction is that it are often activated once information is other or emended or deleted from a table during a info.
What is a view?
– If we’ve many tables during a dB and that we need to look at solely specific columns from specific tables we are able to select views. it might additionally answer the requirements of security some times permitting specfic users to visualize solely specific columns supported the permission that we are able to tack together on the read. Views also reduce the effort that is required for writing queries to access specific columns every time.
SQL Interview Questions – 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.
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.
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.
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.
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.
Which TCP/IP port does SQL Server run on?
– SQL Server runs on port 1433 but we can also change it for better security.
From where can you change the default port?
– From the Network Utility TCP/IP properties < Port number. both on client and the server.
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.
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.
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.
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.
What command do we use to rename a db? – sp_renamedb ‘oldname’ , ‘newname’
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.
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.
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.
What is a Join in SQL Server?
– Join actually puts data from two or more tables into a single result set.
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
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..
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.
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.
Which stored procedure will you be running to add a linked server?
– sp_addlinkedserver, sp_addlinkedsrvlogin
What are the OS services that the SQL Server installation adds? – MS SQL SERVER SERVICE, SQL AGENT SERVICE, DTC (Distribution transac co-ordinator)
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
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 ascertain for the users and current SQL activities and jobs running which could be a retardant. Third would be to run UPDATE_STATISTICS command to update the indexes
Lets say because of N/W or Security problems consumer isn’t ready to hook up with server or contrariwise. how does one troubleshoot?
– 1st i’ll look to confirm that port settings square measure correct on server and consumer Network utility for connections. ODBC is correctly organized at consumer finish for association
——Makepipe & readpipe square measure utilities to ascertain for association. Makepipe is run on Server and readpipe on consumer to ascertain for any association problems.
What square measure the authentication modes in SQL Server?
– Windows mode and mixed mode (SQL & Windows).
Where does one assume the users names and passwords are going to be keep in sql server?
– They get keep in master dB within the sysxlogins table.
What is log shipping? will we have a tendency to do logshipping with SQL Server 7+.
– Logshipping may be a new feature of SQL Server 2000. we must always have 2 SQL Server – Enterprise Editions. From Enterprise Manager we are able to tack together the logshipping. In logshipping the transactional log file from one server is mechanically updated into the backup info on the opposite server. If one server fails, the opposite server can have constant dB and that we will use this because the DR (disaster recovery) set up.
Let us say the SQL Server crashed and you’re reconstruction the infos as well as the master database what procedure to you follow?
– For restoring the master dB we’ve to prevent the SQL Server 1st so from program line we are able to kind SQLSERVER –m which can primarily bring it into the upkeep mode when that we are able to restore the master dB.
Let us say master dB itself has no backup. currently you have got to reconstruct the dB thus what quite action does one take?
– (I am not sure- however i feel we’ve a command to try and do it).
SQL Interview Questions – What is BCP? once will we use it?
– BulkCopy may be a tool wont to copy immense quantity of information from tables and views. however it won’t copy the structures of constant.
What ought to we have a tendency to do to repeat the tables, schema and views from one SQL Server to another?
– we’ve to put in writing some psychosis packages for it.
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