On Wed, Sep 04, 2002 at 09:58:35AM -0500, Paul DuBois wrote:
> At 9:50 -0500 9/4/02, David Dooling wrote:
> >For security reasons, wouldn't you want to know what statements are
> >non-select _before_ you execute?
> >
> >If you only care about after, how about something like this:
> >
> > $sth->execute;
> > my @row = $sth->fetchrow_array;
> > if (@row) { # results }
> > elsif (!$sth->errstr) { # now rows }
> > else { warn $sth->errstr }
> >
> >You can't distinguish between selects that return no data and
> >non-selects. But for your example below, it really wouldn't matter.
> >It seems you need to parse this stuff before.
>
> In MySQL, you can distinguish select from non-select statements after
> $sth->execute by checking $sth->{NUM_OF_FIELDS}. If it's zero, it's
> a non-select, if it's non-zero, it's a select. This works even if the
> select returns zero rows, because the "width" of the result set is
> greater than zero. No parsing of the statement or any other messing
> around with it is necessary.
>
> Does this work for other database engines as well?
It has to as it's the "standard" way to check. The DBI docs specifically
say "Non-C<SELECT> statements will have C<NUM_OF_FIELDS == 0>."
Tim.
