field lengths of database tables

tomgracey has asked for the wisdom of the Perl Monks concerning the following question:

I'm sure this is a pretty easy one, but I've spent a long time searching on the internet and still haven't resolved the problem. I am trying to extract the lengths of the fields from a mysql table using DBI. Based on the documentation I read I wrote this code:

$sth=$dbh->prepare('SELECT * FROM userReports WHERE 1=0');
$sth->execute();

my $flh=$sth->{SCALE};
my @lengths=@{$flh};

print "@lengths";
[download]

If I substitute NAME for SCALE then I get an array of column names as expected. However, using SCALE I just get an array full of zeros. I wonder what the problem with this is? Also, is there a better way of doing this?

Comment on field lengths of database tables Download Code

Replies are listed 'Best First'.
Re: field lengths of database tables by dbwiz (Curate) on Apr 20, 2005 at 07:33 UTC
Instead of SCALE, use PRECISION. Check the DBI docs for some caveats about its applicability with numerical types. To get reliable results, you should use `$sth->{PRECISION}` in coordination with the values of `$sth->{TYPE}`	[reply] [d/l] [select]
Thanks! - Re to field lengths of database tables by polettix (Vicar) on Apr 20, 2005 at 14:51 UTC
I want to thank you for this post. Just yesterday I was wondering how I could get column names, and a first search in DBI docs did not give me a positive answer - go figure where I was looking at :) Update: retitled as per site administrators' suggestion (reason in How do I compose an effective node title?). Flavio (perl -e "print(scalar(reverse('ti.xittelop@oivalf')))") Don't fool yourself.	[reply]
Re: field lengths of database tables by Anonymous Monk on Apr 20, 2005 at 07:50 UTC
SCALE isn't documented in DBD::mysql, try LENGTH	[reply]
Re^2: field lengths of database tables by tomgracey (Beadle) on Apr 20, 2005 at 08:29 UTC
Thanks for the info dbwiz... You're right the array does fill up properly when I use PRECISION, though it does look like a bit of added work is necessary to get the data in the right format. I take it theres no way around this then? BTW Anonymous Monk, I couldn't get LENGTH to work at all, the program just falls over saying 'unrecognised attribute'.	[reply]
Re: field lengths of database tables by kgraff (Monk) on Apr 20, 2005 at 19:40 UTC
A quick and dirty way get table information is send the `describe` MySQL command. It doesn't port well to other databases but gives you most of the information in one query.	[reply] [d/l]


Don't ask to ask, just ask
	PerlMonks