SQL: retrieve only the records whose value has changed

Question

Sorry for the nondescript title. I\'ll edit as we go along.

I have a table RateTable:

| Code   |  Date     |   Rate  |

  B001     2009-         


        

Answer 1

Add a new column which will be a DateTime and track when the rate changed. Then you can just return any columns who DateModified >= x...Where x is the last time you checked.