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field lengths of database tables

by tomgracey (Beadle)
on Apr 20, 2005 at 07:06 UTC ( #449501=perlquestion: print w/replies, xml ) Need Help??

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";
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?

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}

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.
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

      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'.

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.

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