Empty Set

Monolith-0 has asked for the wisdom of the Perl Monks concerning the following question:

Here's a quick question which I can't seem to find the answer to..
How can you tell if a table in the database is empty? All I could think of was something like the following, but obvoiusly that's not right.

my $query= "SELECT id FROM users LIMIT 1";
my $sth=$dbh->do($query) or DBerror();
if ($sth->fetchrow_array == undef) {
   ...
}
[download]

- Monolith

Comment on Empty Set Download Code

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Re: Empty Set by Trimbach (Curate) on Jul 13, 2001 at 07:03 UTC
Maybe a little simpler (and optimized on many databases) is `my $query = "SELECT count(*) FROM table";` [download] This will return true if there are any rows of any kind in the table. Gary Blackburn Trained Killer	[reply] [d/l]
Re: Empty Set by VSarkiss (Monsignor) on Jul 13, 2001 at 07:16 UTC
Empty table == no rows. Therefore: `my $query = "SELECT count() FROM users";`Some databases will store the count in the catalog (Informix used to) and will return very* quickly. Some will count quickly if you have a clustered index on the table. Some will just count every row.... HTH	[reply] [d/l]
Re: Empty Set by Monolith-0 (Beadle) on Jul 13, 2001 at 07:21 UTC
Ah, I didn't remember count(). Thanks, to both of you. :)	[reply]