Missing Index

I was trying to identify the missing indexes in my SQL Server 2012 database and I used the Display Estimated Execution Plan in the SQL Server Management Studio. Even after I created the suggested index, succeeding attempts to display the execution plan still showed the index that I just created as missing.

SQL Server keeps data about possible missing indexes and the script below helped me to show all the missing indexes that SQL Server was tracking as well as the actual scripts to create these missing indexes. I got it from this link:

http://blog.sqlauthority.com/2011/01/03/sql-server-2008-missing-index-script-download/

SELECT

dm_mid.database_id AS DatabaseID,

dm_migs.avg_user_impact*(dm_migs.user_seeks+dm_migs.user_scans) Avg_Estimated_Impact,

dm_migs.last_user_seek AS Last_User_Seek,

OBJECT_NAME(dm_mid.OBJECT_ID,dm_mid.database_id) AS [TableName],

'CREATE INDEX [IX_' + OBJECT_NAME(dm_mid.OBJECT_ID,dm_mid.database_id) + '_'

+ REPLACE(REPLACE(REPLACE(ISNULL(dm_mid.equality_columns,''),', ','_'),'[',''),']','') +

CASE

WHEN dm_mid.equality_columns IS NOT NULL AND dm_mid.inequality_columns IS NOT NULL THEN '_'

ELSE ''

END

+ REPLACE(REPLACE(REPLACE(ISNULL(dm_mid.inequality_columns,''),', ','_'),'[',''),']','')

+ ']'

+ ' ON ' + dm_mid.statement

+ ' (' + ISNULL (dm_mid.equality_columns,'')

+ CASE WHEN dm_mid.equality_columns IS NOT NULL AND dm_mid.inequality_columns IS NOT NULL THEN ',' ELSE

'' END

+ ISNULL (dm_mid.inequality_columns, '')

+ ')'

+ ISNULL (' INCLUDE (' + dm_mid.included_columns + ')', '') AS Create_Statement

FROM sys.dm_db_missing_index_groups dm_mig

INNER JOIN sys.dm_db_missing_index_group_stats dm_migs

ON dm_migs.group_handle = dm_mig.index_group_handle

INNER JOIN sys.dm_db_missing_index_details dm_mid

ON dm_mig.index_handle = dm_mid.index_handle

WHERE dm_mid.database_ID = DB_ID()

ORDER BY Avg_Estimated_Impact DESC

GO

In my case, I saw multiple suggestions for missing indexes for the same table I was having trouble on. When I created all the suggested indexes, the problem with the Display Estimated Execution Plan query did not appear anymore and the performance of the query was great.