How do I know how many rows a Perl DBI query returns?

Question

I'm trying to basically do a search through the database with Perl to tell if there is an item with a certain ID. This search can return no rows, but it can also return one.

I have the following code:

my $th = $dbh->prepare(qq{SELECT bi_exim_id FROM bounce_info WHERE bi_exim_id = '$exid'});
$th->execute();
if ($th->fetch()->[0] != $exid) {
        ...

Basically, this tries to see if the ID was returned and if it's not, continue with the script. But it is throwing a Null array reference error on the $th->fetch()->[0] thing. How can i just simply check to see if it returned rows or now?

Answer 1

The DBD::mysql driver has a the rows() method that can return the count of the results:

$sth = $dbh->prepare( ... );
$sth->execute;
$rows = $sth->rows;

This is database-driver specific, so it might not work in other drivers, or it might work differently in other drivers.