DBI: bind_param casts string to ntext -> nvarchar(max) and ntext are incompatible

Question

I have a problem concerning perl DBI's bind_param. The following SQL works:

my $sth = $dbh->prepare("SELECT id FROM table WHERE id = 'string'");
$sth->execute();

While the following doesn't:

my $sth = $dbh->prepare("SELECT id FROM table WHERE id = ?");
$sth->execute('string');

The error the last query causes is:

[ODBC SQL Server Driver][SQL Server]The data types nvarchar(max) and ntext are incompatible in the equal to operator. (SQL-42000)

It seems like bind_param, which gets called by execute, casts 'string' to ntext. How can I work around that?

Answer 1

Consider binding the value type prior the SQL call:

use DBI qw(:sql_types);

my $sth = $dbh->prepare( "SELECT id FROM table WHERE id = ?" );

my $key = 'string';
my $sth->bind_param( 1, $key, SQL_VARCHAR );

$sth->execute();