sql-faq-3

29. 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.

30. 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.

31. 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.

32. What are the authentication modes in SQL Server?
Windows mode and mixed mode (SQL & Windows).

33. 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.

34. 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.

35. 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.

36. 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).

37. 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.

38. Write a SQL Query to find first Week Day of month?
SELECT
DATENAME(dw, DATEADD(dd, - DATEPART(dd, GETDATE()) + 1, GETDATE())) AS FirstDay


39. How to find 6th highest salary from Employee table
SELECT TOP 1 salary
FROM (SELECT DISTINCT TOP 6 salary
FROM employee
ORDER BY salary DESC)
ORDER BY salary


40. What is a join and List 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.