DB2 replace into实现

    public function replace($table, $arr, $pks){
        $values = '';
        $keys = '';
        $mergeValues = '';
        $upStatement = '';
        $first = true;
        foreach($arr as $key => $val){
            if (!$first){
                $values .= ',';
                $keys .= ',';
                $mergeValues .= ',';
                $upStatement .= ',';
            }
            else{
                $first = false;
            }
            $values .= "'{$val}'";
            $keys .= $key;
            $mergeValues .= "merge.{$key}";
            $upStatement .= "tab.{$key} = merge.{$key}";
        }
        $first = true;
        $pkstr = '';
        foreach($pks as $pk){
            if (!$first){
                $pkstr .= ' AND ';
            }
            else{
                $first = false;
            }
            $pkstr .= "tab.{$pk} = merge.{$pk}";
        }
        $sql = "MERGE INTO {$table} AS tab
        USING (VALUES
        ({$values})
        ) AS merge ({$keys})
        ON {$pkstr}
        WHEN MATCHED THEN
        UPDATE SET {$upStatement}
        WHEN NOT MATCHED THEN
        INSERT ({$keys})
        VALUES ({$mergeValues})";
        $this->db->query($sql);
    }