Intrepret the results of the index usage query

I have 开发者_StackOverflowadded an index for a table in sql server 2008. I would like to know how much impact the index has on the table and if the index is useful or not.

Thanks.

The best way to tell is to look at execution plans for queries run against the table.

You can look at index usage DMVs but they only tell you how many queries used the index. Whether that is a one-row seek or a 10 million row scan, there's no difference in the recorded stats.

Did you make any measurments prior to making the change? If you did a baseline measurment prior to modifing the system run the same baseline then compare the results.

Two things the DMVs for indexes can tell use is how much the index is used to satisfy queries and how much it cost to keep an index. As the ratio (index usage / index) updates gets smaller the more time the DBA should take in deciding if the index is needed.