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Home -> Community -> Usenet -> c.d.o.misc -> Re: Performance effect of number of columns on SELECT clause?
Pasi Kovanen wrote:
>
> We did some tests using different SELECT clauses and were
> surprised to found how much the number of columns that
> were selected affect the performance.
>
> For example, execution time of
> SELECT column1 from foobar
> seems to be almost constant whatever the size of data returned in
> column1 is 20 - 400 bytes (only 5% decrease w/ 400 bytes).
>
> Wheres
> SELECT column1, column2, ... column13 from foobar can take
> even 40% longer though mo
Is perhaps column1 indexed ? Try it with
SQL> set autotrace on
and see if you get the same explain plan for each.
hth
connor
-- ============================== Connor McDonald http://www.oracledba.co.uk "Some days you're the pigeon, some days you're the statue..."Received on Wed Feb 27 2002 - 16:12:21 CST