Index Covering Boosts SQL Server Query Performance
Index covering is a quick and easy solution to many query performance problems. By just adding a column or two to an index you can significantly boost a query's performance.
by Alexander Kuznetsov
October 20, 2005
reating a non-clustered index that contains all the columns used in a SQL query, a technique called index covering, is a quick and easy solution to many query performance problems. Sometimes just adding a column or two to an index can really boost the query's performance. Check out a couple of all-too-common scenarios where applying index covering can speed up the queries in your Microsoft SQL Server database.
Scenario 1: Speed Up a Query for a Table with a Clustered Index
Consider a very typical scenario: you have a table ORDERS with a clustered index on CUSTOMER_ID column. You need to speed up a select query quickly:
SELECT ORDER_DATE, SUM(AMOUNT) FROM ORDERS GROUP BY ORDER_DATE
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reating a non-clustered index that contains all the columns used in a SQL query, a technique called index covering, is a quick and easy solution to many query performance problems. Sometimes just adding a column or two to an index can really boost the query's performance. Check out a couple of all-too-common scenarios where applying index covering can speed up the queries in your Microsoft SQL Server database.
