public function getDropConstraintSQL($constraint, $table)
    {
        if (! $constraint instanceof Constraint) {
            $constraint = new Identifier($constraint);
        }

        if (! $table instanceof Table) {
            $table = new Identifier($table);
        }

        $constraint = $constraint->getQuotedName($this);
        $table      = $table->getQuotedName($this);

        return 'ALTER TABLE ' . $table . ' DROP CONSTRAINT ' . $constraint;
    }