I'm writing a script to print out all of the tables in a database and
the column descriptions of each table. So far, I have the following:


#!/usr/bin/perl -w

use DBI;

my $sqldriver = DBI->install_driver('mysql');

my $dbh = DBI->connect('DBI:mysql:books:localhost', 'name', 'password');

if(!$dbh) {
die "Can't find database!";
}

$tables = $dbh->selectall_arrayref('show tables;');

foreach $table(@$tables){
print "\n\n@$table\n";
$columns = $dbh->selectall_arrayref("show columns from @$table");
foreach $column(@$columns){
print "@$column\n"; #line 19
}
}



The output I get is:

Author
Use of uninitialized value in join or string at ./printtables.pl line
19.
AuthorID int(11) PRI auto_increment
LastName varchar(50)
Use of uninitialized value in join or string at ./printtables.pl line
19.
FirstName varchar(50) YES
Use of uninitialized value in join or string at ./printtables.pl line
19.
MiddleName varchar(50) YES


Binding
Use of uninitialized value in join or string at ./printtables.pl line
19.
BindingID int(11) PRI auto_increment
Use of uninitialized value in join or string at ./printtables.pl line
19.
BindingType varchar(25) YES

....


What is causing the "Use of unititialized value..." errors?


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Dan Jones wrote:

Most probably you have NULL values in your table, which are translated
to nulls. Try replacing

print "@$column\n";

with

print join("", map{defined($_) ? $_ : ""} @$columns), "\n";


Jochen


P.S: And do not forget to 'use "strict"' :-)


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