1. Use stored procedures instead of heavy-duty queries.
This can reduce network traffic as your client will send to the server only the stored procedure name (perhaps with some parameters) instead of all the text from a large heavy-duty query. Stored procedures can be used to enhance security and conceal underlying data objects as well. For example, you can give the users permission to execute the stored procedure to work with restricted sets of columns and data.
2. Include the SET NOCOUNT ON statement in your stored procedures to stop the message indicating the number of rows affected by a Transact-SQL statement.
This can reduce network traffic due to the fact that your client will not receive the message indicating the number of rows affected by a Transact-SQL statement.
3. Call stored procedures using their fully qualified name.
The complete name of an object consists of four identifiers: the server name, database name, owner name, and object name. An object name that specifies all four parts is known as a fully qualified name.
Using fully qualified names eliminates any confusion about which stored procedure you want to run and can boost performance because SQL Server has a better chance to reuse the stored procedures execution plans if they were executed using fully qualified names.
4. Consider returning the integer value as a RETURN statement instead of returning an integer value as part of a recordset.
The RETURN statement exits unconditionally from a stored procedure, so the statements following RETURN are not executed. Though the RETURN statement is generally used for error checking, you can use this statement to return an integer value for any other reason. Using the RETURN statement can boost performance because SQL Server will not create a recordset.
5. Don't use the prefix "sp_" in the stored procedure name if you need to create a stored procedure to run in a database other than the master database.
The prefix "sp_" is used in the system stored procedures names. Microsoft does not recommend using the prefix "sp_" in user-created stored procedure names as SQL Server always looks for a stored procedure beginning with "sp_" in the following order: the master database, the stored procedure based on the fully qualified name provided, followed by the stored procedure using dbo as the owner (if one is not specified).
When you have the stored procedure with the prefix "sp_" in a database other than master, the master database is always checked first. If the user-created stored procedure has the same name as a system stored procedure, the user-created stored procedure will never be executed.
6. Use the sp_executesql stored procedure instead of the EXECUTE statement.
The sp_executesql stored procedure supports parameters. So, using the sp_executesql stored procedure instead of the EXECUTE statement improves readability of your code when many parameters are used.
When you use the sp_executesql stored procedure to execute a Transact-SQL statement that will be reused many times, the SQL Server query optimizer will reuse the execution plan it generates for the first execution when the change in parameter values to the statement is the only variation.
7. Use the sp_executesql stored procedure instead of temporary stored procedures.
Microsoft recommends using temporary stored procedures when connecting to earlier versions of SQL Server that do not support the reuse of execution plans. Applications connecting to SQL Server 7.0 or SQL Server 2000 should use the sp_executesql system stored procedure instead of temporary stored procedures in order to have a better chance of reusing the execution plans.
8. If you have a very large stored procedure, try to break down the stored procedure into several sub-procedures, and call them from a controlling stored procedure.
The stored procedure will be recompiled when any structural changes are made to a table or view referenced by the stored procedure (an ALTER TABLE statement, for example), or when a large number of INSERTS, UPDATES or DELETES are made to a table referenced by a stored procedure. So, if you break down a very large stored procedure into several sub-procedures, there's a chance that only a single sub-procedure will be recompiled, while other sub-procedures will not.
9. Try to avoid using temporary tables inside your stored procedures.
Using temporary tables inside stored procedures reduce the chance to reuse the execution plan.
10. Try to avoid using DDL (Data Definition Language) statements inside your stored procedure.
Using DDL statements inside stored procedures also reduce the chance to reuse the execution plan.
11. Add the WITH RECOMPILE option to the CREATE PROCEDURE statement if you know that your query will vary each time it is run from the stored procedure.
The WITH RECOMPILE option prevents reusing the stored procedure execution plan, so SQL Server does not cache a plan for this procedure and the procedure is always recompiled at run time. Using the WITH RECOMPILE option can boost performance if your query will vary each time it is run from the stored procedure, because in this case the wrong execution plan will not be used.
12. Use SQL Server Profiler to determine which stored procedures have been recompiled too often.
To check if a stored procedure has been recompiled, run SQL Server Profiler and choose to trace the event in the "Stored Procedures" category called "SP:Recompile". You can also trace the event "SP:StmtStarting" to see at what point in the procedure it is being recompiled. When you identify these stored procedures, you can take some correction actions to reduce or eliminate the excessive recompilations.
13. Use IF EXISTS (SELECT 1) instead of (SELECT *):
To check the existence of a record in another table, we uses the IF EXISTS clause. The IF EXISTS clause returns True if any value is returned from an internal statement, either a single value “1” or all columns of a record or complete recordset. The output of the internal statement is not used. Hence, to minimize the data for processing and network transferring, we should use “1” in the SELECT clause of an internal statement, as shown below:
IF EXISTS (SELECT 1 FROM sysobjects
WHERE name = 'MyTable' AND type = 'U')
14. Try to avoid using SQL Server cursors whenever possible:
Cursor uses a lot of resources for overhead processing to maintain current record position in a recordset and this decreases the performance. If we need to process records one-by-one in a loop, then we should use the WHILE clause. Wherever possible, we should replace the cursor-based approach with SET-based approach. Because the SQL Server engine is designed and optimized to perform SET-based operation very fast. Again, please note cursor is also a kind of WHILE Loop.
15. Keep the Transaction as short as possible:
The length of transaction affects blocking and deadlocking. Exclusive lock is not released until the end of transaction. In higher isolation level, the shared locks are also aged with transaction. Therefore, lengthy transaction means locks for longer time and locks for longer time turns into blocking. In some cases, blocking also converts into deadlocks. So, for faster execution and less blocking, the transaction should be kept as short as possible.
T16. Use TRY-Catch for error handling
