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

If I read this right, you aren't looking for modified rows, but rows where the rate changes from the previous date. This query or something like it should do it:

SELECT  r1.Code, r1.Date, r1.Rate
FROM    RateTable r1
WHERE   r1.Rate <> (SELECT TOP 1 Rate
                   FROM    RateTable
                   WHERE   Date < r1.Date
                   ORDER BY Date DESC)