• Tac11 (5/18/2016)


    Jack, you said "Another way to explain it that the included columns should be columns that you don't search on, but will return" , I got it, thanks for that. But what about Covering index? can you explain in same way please?

    I see a covering index as one in which all the data needed to support a given query exists in the index. This could be a combination of indexed columns and included columns. Prior to SQL Server 2005 adding the INCLUDE columns to non-clustered indexes this limited covering indexes to 16 columns or 900 bytes, which ever occurred first.