Re: Group By Questions..

In my opinion the result should be the same ? It better be. Using indexes you get the best performance on the same index expresion as the grouping
Without indexes, performance is best if you start with the smallest expected result set from left to right.
Ted

Jimmy wrote:

> Hello all,
>
> Assume I have a table with column A, B, C and D.
>
> I wonder the following SQL statements will produce the same results:
>
> i) select B, C, D, avg(A) from AAA group by B, C, D;
> ii) select B, C, D, avg(A) from AAA group by B, D, C;
> iii) select B, C, D, avg(A) from AAA group by C, B, D;
> ....
>
> i.e. does the order of group by clause affect the final result (or
> performance, if any) of the SQL statement? Anyone knows white papers or
> documents discussing this issue?
>
> Thanks,
> Jimmy

Received on Fri Oct 01 1999 - 14:46:47 CDT