Sql Server Query Optimization Tips

Sql Server Query Optimization Tips

• Use views and stored procedures instead of heavy-duty queries.

This can reduce network traffic, because your client will send to

server only stored procedure or view name (perhaps with some

parameters) instead of large heavy-duty queries text. This can be used

to facilitate permission management also, because you can restrict

user access to table columns they should not see.

• Try to use constraints instead of triggers, whenever possible.

Constraints are much more efficient than triggers and can boost

performance. So, you should use constraints instead of triggers,

whenever possible.

• Use table variables instead of temporary tables.

Table variables require less locking and logging resources than

temporary tables, so table variables should be used whenever possible.

The table variables are available in SQL Server 2000 only.

• Try to use UNION ALL statement instead of UNION, whenever possible.

The UNION ALL statement is much faster than UNION, because UNION ALL

statement does not look for duplicate rows, and UNION statement does

look for duplicate rows, whether or not they exist.

• Try to avoid using the DISTINCT clause, whenever possible.

Because using the DISTINCT clause will result in some performance

degradation, you should use this clause only when it is necessary.

• Try to avoid using SQL Server cursors, whenever possible.

SQL Server cursors can result in some performance degradation in

comparison with select statements. Try to use correlated sub-query or

derived tables, if you need to perform row-by-row operations.

• Try to avoid the HAVING clause, whenever possible.

The HAVING clause is used to restrict the result set returned by the

GROUP BY clause. When you use GROUP BY with the HAVING clause, the

GROUP BY clause divides the rows into sets of grouped rows and

aggregates their values, and then the HAVING clause eliminates

undesired aggregated groups. In many cases, you can write your select

statement so, that it will contain only WHERE and GROUP BY clauses

without HAVING clause. This can improve the performance of your query.

• If you need to return the total table's row count, you can use

alternative way instead of SELECT COUNT(*) statement.

Because SELECT COUNT(*) statement make a full table scan to return the

total table's row count, it can take very many time for the large

table. There is another way to determine the total row count in a

table. You can use sysindexes system table, in this case. There is

ROWS column in the sysindexes table. This column contains the total

row count for each table in your database. So, you can use the

following select statement instead of :-

SELECT COUNT(*): SELECT rows
FROM sysindexes WHERE id = OBJECT_ID('table_name') AND indid < 2 So,

you can improve the speed of such queries in several times.

• Include SET NOCOUNT ON statement into your stored procedures to stop

the message indicating the number of rows affected by a T-SQL statement.

This can reduce network traffic, because your client will not receive

the message indicating the number of rows affected by a T-SQL statement.

• Try to restrict the queries result set by using the WHERE clause.

This can results in good performance benefits, because SQL Server will

return to client only particular rows, not all rows from the table(s).

This can reduce network traffic and boost the overall performance of

the query.

Thanks for Reading Friends ...

You can also see :  SQL Server Frequently Asked Question