DBD::mysql::st execute failed: Unknown column - mysql

Question

When I do the query below from a mysql console it works fine but when I wrap into perl/DBI I get:
DBD::mysql::st execute failed: Unknown column 'AR_email' in 'field list'
Here is the query:
my $q = "SELECT SUBSTRING(AR_email, LOCATE('#', AR_email) + 1) AS domain
FROM carrier
WHERE AR_email IS NOT NULL
AND SUBSTRING(AR_email, LOCATE('#', AR_email) + 1) =?";
my $sth=$dbh->prepare($q);
$sth->execute($domain);
Any idea how I can fix this?

Answer 1

The problem here is unintented string interpolation.
You are using double quotes (") when assigning the query string to $q, but it contains an arobas (#), which is interpolated.
So $q actually ends up containing:
SELECT SUBSTRING(AR_email, LOCATE(', AR_email) + 1) AS domain
FROM carrier
WHERE AR_email IS NOT NULL
AND SUBSTRING(AR_email, LOCATE(', AR_email) + 1) =?
If you were running this under use warnings, you would get this message:
Possible unintended interpolation of #' in string
One way to solve this is to define the query as a litteral string, for example:
my $q = q/SELECT SUBSTRING(AR_email, LOCATE('#', AR_email) + 1) AS domain
FROM carrier
WHERE AR_email IS NOT NULL
AND SUBSTRING(AR_email, LOCATE('#', AR_email) + 1) =?/;
Moral of the story:
use double quotes only when you do want string interpolation
always use strict; use warnings;