SQL Server - how to determine if indexes aren't being used?

Question

I have a high-demand transactional database that I think is over-indexed. Originally, it didn\'t have any indexes at all, so adding some for common processes made a huge differe

Answer 1

This script will look at the DMV's (dynamic management views) and find those indices that haven't been used.

DECLARE  @dbid INT

SELECT @dbid = DB_ID(DB_NAME())

SELECT   
    OBJECTNAME = OBJECT_NAME(I.OBJECT_ID),
    INDEXNAME = I.NAME,
    I.INDEX_ID
FROM     
    SYS.INDEXES I
JOIN 
    SYS.OBJECTS O ON I.OBJECT_ID = O.OBJECT_ID
WHERE    
    OBJECTPROPERTY(O.OBJECT_ID, 'IsUserTable') = 1
    AND I.INDEX_ID NOT IN 
       (SELECT S.INDEX_ID
        FROM SYS.DM_DB_INDEX_USAGE_STATS S
        WHERE S.OBJECT_ID = I.OBJECT_ID
        AND I.INDEX_ID = S.INDEX_ID
        AND DATABASE_ID = @dbid)
ORDER BY 
    OBJECTNAME, I.INDEX_ID, INDEXNAME ASC

Mind you - the DMV are dynamic - e.g. they get reset to "nothing" every time you restart your SQL Server services. Don't check those if your server has been up for only a few minutes! Almost all indices will show up in your result set......

But if you can monitor the result set of this query over time, you should definitely get a feel for which indices aren't being used ever. Very handy indeed !