[thelist] CF & SQL: Selecting unique months from date column

rudy rudy937 at rogers.com
Thu Jul 17 19:12:24 CDT 2003


> > SELECT Month(DateColumn), Year(DateColumn)
> > FROM TableName
> > GROUP BY Year(DateColumn), Month(DateColumn)
>
> > (the order of the GROUP BY clause is important)
>
> Tab,
>
> Why is the ordering in the GROUP BY clause important in this query?

short answer:  it isn't

long answer:  because all other things being equal -- i know, i know,
sometimes they aren't -- the GROUP BY sequence of columns is the sort order
the groups will be returned in

saves an explicit ORDER BY

occasionally this can make a big difference in performance of large queries


rudy



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