Question

我有一个表，其中每个记录包含他的父亲，这个层次结构最多可以有6个级别。下面的查询搜索名为＆＃34; DEPARTMENT ABCD＆＃34;的部门的所有父母。此查询完美无缺。

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，如果我想同时获取多个孩子的父母（使用类似下面的查询），我会收到错误：＆＃34;错误代码：1242。子查询返回超过1行＆＃34;

查询错误＆＃34;子查询返回多行＆＃34;：

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;

我怎样才能同时接收一个以上孩子的父母？

我在SQL小提琴中添加了一个示例：http://sqlfiddle.com/#!9/f182fb/3

Answer 1

鉴于层次结构最多可能有6个级别，我建议加入该表6次，以获得所选部门的所有祖先：

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

Mysql - 如何选择子列表中的所有父项？

1 个答案: