Mysql 获取父id为null的记录，并用“父id”=id的记录替换数据

我有一张桌子：

+-------+-------------+-----------+-------------+
| ID    | parent_id   | name      | other_data  | 
+-------+-------------+-----------+-------------+
| 1     |  null       | name      | ...         |
| 2     |  null       | name1     | ...         |
| 3     |  null       | name2     | ...         |
| 4     |  2          | name1new  | ...         |
| 5     |  3          | name2new  | ...         |
| 6     |  3          | name2new2 | ...         |
+-------+-------------+-----------+-------------+  

我需要所有父项id为空的记录。简单查询可以如下所示：

    SELECT id, name
        FROM  `table` 
        WHERE  `parent_id` IS NULL 
        LIMIT 0 , 30

它将返回3条记录：

 1 name;
 2 name1;
 3 name2

我想要的是获得这3条记录，但用来自元素的新值替换第二条记录，这些元素的父id为当前id，例如，第4行具有父id 2，因此第二行中的新数据必须来自第4行。但两者都有：第5行和第6行都有父_id 3，所以第3行必须有来自第6行的数据-较新的数据。 我需要这样的结果：

1 name; 
4 name1new;
6 name2new2;

已解决：

SELECT
(CASE WHEN  `t2`.`parent_id` is NOT NULL THEN `t2`.`id` ELSE `t1`.`id` END) as `new_id`,
(CASE WHEN  `t2`.`parent_id` is NOT NULL THEN `t2`.`name` else `t1`.`name` END) as `new_name`
FROM `table` as `t1` LEFT JOIN `table` as `t2` on (`t1`.`id` = `t2`.`parent_id` AND `t2`.`some_id` = '6') WHERE `t1`.`parent_id` IS NULL;

THX寻求帮助@Vishal Zanzrukia

试试这个：

---

我得到了一个错误：MySQL服务器版本的正确语法使用了near'case when t2.parent_id不为null，然后t2.name else t1.name end as new_name fr'在第3行，对此表示担忧。立即尝试：获得相同的错误。但是如果我在新的id后面用逗号就可以了。但是要找到mutch记录：1个名字；4.名称1新；5名2名新成员；6.2新名称；1248-每个派生表都必须有自己的别名-erroroh再次为语法错误感到抱歉：检查更新的ans：如果有帮助，您应该接受答案：I will。但是您应该删除错误：P

$sql="select parent_id,name from table where parent_id  IS NOT NULL  group by parent_id";
while($r= mysql_fetch_array(mysql_query($sql))){
    $sql2="update table set name='$r[name]' where ID=$r[parent_id]  and parent_id  IS NULL ";
    mysql_query($sql2);

}

select 
tmp1.new_id,
tmp1.new_name
from
(select
    (case when  t2.parent_id is not null then t2.ID else t1.ID end) as new_id,
    (case when  t2.parent_id is not null then t2.name else t1.name end) as new_name,
    (case when  t2.parent_id is not null then t2.parent_id else concat(t1.id,t1.name) end) as parent_id
    from table t1 left join table t2 on t1.ID = t2.parent_id group by new_id) tmp1
left join
(select
    (case when  t2.parent_id is not null then t2.ID else t1.ID end) as new_id,
    (case when  t2.parent_id is not null then t2.name else t1.name end) as new_name,
    (case when  t2.parent_id is not null then t2.parent_id else concat(t1.id,t1.name) end) as parent_id
    from table t1 left join table t2 on t1.ID = t2.parent_id group by new_id) tmp2
on (tmp1.parent_id = tmp2.parent_id and tmp1.new_id < tmp2.new_id)
where tmp2.new_id is null
;