Lian

Be careful with missing index recommendations. They only suggest indexes that would improve performance on individual queries, not on the workload as a whole.

Adding an included column to an index can improve performance more than adding the same column to the index key. This is because, since the values are only stored at leaf level, it takes fewer writes to maintain and fewer reads to return data. You will only want to do this if the column is being added to cover a query, not if it is being used in a search operation such as a WHERE clause or a JOIN predicate.

John