LazyRecord\SqlBuilder\MysqlBuilder::buildForeignKeyConstraint PHP Method

    public function buildForeignKeyConstraint(Relationship $rel)
    {
        $schemaClass = $rel['foreign_schema'];
        $fSchema = new $schemaClass();
        $constraint = new Constraint();
        $constraint->foreignKey($rel['self_column']);
        $references = $constraint->references($fSchema->getTable(), (array) $rel['foreign_column']);
        if ($act = $rel->onUpdate) {
            $references->onUpdate($act);
        }
        if ($act = $rel->onDelete) {
            $references->onDelete($act);
        }
        return $constraint;
    }