>I have the following SQL Select that looks for the last order number:
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>select top 1 order_no from order_file where REC_ID <> 'D' order by order_no desc
>

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>The column ORDER_NO is the Primary key and Identity. But I noticed in SSMS that this column does not have an Index. Do I need to create an index for this column or the fact that it is Primary key already created an index?
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>Also, would creating an index on column REC_ID speed up the above SQL Select?

Create a compound index on REC_ID with included field Order_No.

Then, put that select in a query window and show the execution plan. It should use this index.