sys.dm_db_missing_index_details results

  • I've run the sys.dm_db_missing_index_details and I've found out the results. These are all coming on the same table A.

    equality_columns inequality_columns included_columns

    [CAL_RUN_ID] [PYMT_DT] [EMPLID], [EMPL_RCD],[COUNTRY]

    [CAL_RUN_ID] [EMPLID], [PYE_PRC_IND], [SEL_STAT] [COUNTRY]

    [CAL_RUN_ID], [PYE_PRC_IND] [EMPLID] [COUNTRY]

    *** Question: Do I have to run all these indexes against table A?

    Can't I just run 1 index that would contain the Cal_Run_ID, Pye_Prc_Ind on the equality_columns and the inequality_columns will contain the pymt_dt, emplid, sel_stat and included_columns will be country?

    Could please someone help me out interpret the results?

    Thank you.

  • Those are all different indexes because the column order is different.

    See http://www.sqlservercentral.com/articles/Indexing/68439/ and http://www.sqlservercentral.com/articles/Indexing/68636/

    That said, you should never automatically add indexes that missing indexes suggests. Test each one (on a test server) see if it makes a difference, see if it makes enough of a difference, implement it only if it's useful enough (remember more indexes means more space, more overhead on DML, more time for maintenance)

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

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