Mysql - 如何选择所有父母的孩子列表？

Question

我有一个表，其中每个记录包含他的父亲，这个层次可能有多达6个级别。以下查询搜索名为“DEPARTMENT ABCD”的部门的所有家长。此查询完美工作。

SELECT D2.id, D2.name, D2.id_parent 
FROM (
    SELECT 
     @d AS _id, 
     (SELECT @d := id_parent FROM department WHERE id = _id) AS id_parent, 
     @l := @l + 1 AS level 
    FROM 
     (SELECT 
      @d := (select id from department where name = 'DEPARTMENT ABCD'), 
      @l := 0 
     ) initial_level, 
     department D 
    WHERE @d <> 0 
) D1 
JOIN department D2 ON D1._id = D2.id 
ORDER BY D1.level DESC; 

但是，如果我想在同一时间获得超过一个孩子的父母（使用类似下面的查询），我得到的错误：“错误代码：1242子查询返回多个1行”。

查询并显示错误“子查询返回多个1行”：

SELECT D2.id, D2.name, D2.id_parent 
FROM (
    SELECT 
     @d AS _id, 
     (SELECT @d := id_parent FROM department WHERE id = _id) AS id_parent, 
     @l := @l + 1 AS level 
    FROM 
     (SELECT 
      @d := (select id from department where name like 'DEPARTMENT %A%'), 
      @l := 0 
     ) initial_level, 
     department D 
    WHERE @d <> 0 
) D1 
JOIN department D2 ON D1._id = D2.id 
ORDER BY D1.level DESC; 

我怎么能这样做的同时获得超过一个孩子的父母？

我加入SQL小提琴样本：http://sqlfiddle.com/#!9/f182fb/3

Answer 1

鉴于层次可能有多达6级，我建议加入表6倍，以获得所选择的部门的所有祖先：

select  distinct id, name, id_parent 
from  (
      select  d6.id_parent as id6, 
         d5.id_parent as id5, 
         d4.id_parent as id4, 
         d3.id_parent as id3, 
         d2.id_parent as id2, 
         d1.id_parent as id1, 
         d1.id  as id0 
      from  department d1 
      left join department d2 on d2.id = d1.id_parent 
      left join department d3 on d3.id = d2.id_parent 
      left join department d4 on d4.id = d3.id_parent 
      left join department d5 on d5.id = d4.id_parent 
      left join department d6 on d6.id = d5.id_parent 
      where  d1.name like 'DEPARTMENT A%' 
      ) as h 
inner join department d on d.id in (id0, id1, id2, id3, id4, id5, id6) 
order by 1; 

SQL fiddle