my $sql='UPDATE products SET sku=? WHERE sku=?';
my $sql_values = [$sku, $old_sku];
$dbh->do($sql, undef, $sql_values);

##</code><code>##

DBD::mysql::db do failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1 at ...

##</code><code>##

my $sql='UPDATE products SET sku="'.$sku.'" WHERE sku="'.$old_sku.'"';
$dbh->do($sql);