my $sth = dbh->prepare(
'UPDATE phone_avail SET svcnum = NULL
WHERE svcnum IS NOT NULL
- AND 0 = ( SELECT COUNT(*) FROM svc_phone
- WHERE phone_avail.svcnum = svc_phone.svcnum )'
+ AND NOT EXISTS ( SELECT 1 FROM svc_phone
+ WHERE phone_avail.svcnum = svc_phone.svcnum )'
) or die dbh->errstr;
$sth->execute or die $sth->errstr;