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Re: Getting column size/type From DBI

by arturo (Vicar)
on Jul 22, 2002 at 17:20 UTC ( #184137=note: print w/replies, xml ) Need Help??


in reply to Getting column size/type From DBI

The DBI defines methods for getting metadata. If you want to get info on a given table, though, you have to go through a statement handle. It's a little bit involved after that. You execute a "select * from table_name" (or, if you know the field names you're interested in, just get those) and then the driver makes other info available to you via the {NAME} and {TYPE} attributes of the statement handle.

The *statement handle* attribute {NAME} is a reference to an array of the names of the fields returned by the current statement, and there's also the Probably the most straightforward way of doing this looks something like this:
# you've already got your DB handle: my @tables = $db->tables(); foreach my $table (@tables) { my $sql = "select * from $table"; my $sth = $db->prepare( $sql ); $sth->execute(); # check for errors, either set RaiseError or have + a "die" clause here print "Structure of $table \n\n"; my $num_fields = $sth->{NUM_OF_FIELDS}; for ( my $i=0; $i< $num_fields; $i++ ) { my $field = $sth->{NAME}->[$i]; my $type = $sth->{TYPE}->[$i]; my $precision = $sth->{PRECISION}->[$i]; # e.g. VARCHAR(50) ha +s a precision of 50 print "Field $field is of type $type, with precision $ precisi +on\n"; } $sth->finish(); }

You can turn those numeric types into more descriptive names, I don't know anything specifically about DBI::Pg, and my knowledge is derived from the very useful Programming the Perl DBI, which has been surpassed on the metadata issue via newer versions of the DBI, but I see that those newer versions of the DBI define type_info methods that can help you figure out which types you're dealing with.

HTH.

I mistrust all systematizers and avoid them. The will to a system shows a lack of integrity -- F. Nietzsche

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