Hi,

You should always keep the indexing key as narrower as possible. However, sometimes you could use one index to cover more queries. In your case you plan to use only the Transaction_Date column in the key list, and include the other columns. If the execution plan does not detect missing indexes, then it'll keep on that way regardless of the table size. It will be better if you can overview some other queries to possibly extend the key and the include list, but always try to keep narrower the key list for faster navigation. The extension of the include list increases the index's size and does not have impact on the index's seeking speed.

Regards,

Igor