单纯MYSQL递归查询上下级关系

查询 id = 6 的所有父级

SELECT ID.level, DATA.* FROM(
SELECT
@id as _id,
( SELECT @id := parent_id
FROM table1
WHERE id = @id
) as _pid,
@l := @l+1 as level
FROM table1,
(SELECT @id := 6, @l := 0 ) b
WHERE @id > 0
) ID, table1 DATA
WHERE ID._id = DATA.id
ORDER BY level;

根据这个父级查询方法，很容易可以写出查所有子级的，下面的查询 id=3 的所有子级

SELECT ID.level, DATA.* FROM(
SELECT
@ids as _ids,
( SELECT @ids := GROUP_CONCAT(id)
FROM table1
WHERE FIND_IN_SET(parent_id, @ids)
) as cids,
@l := @l+1 as level
FROM table1,
(SELECT @ids :=3, @l := 0 ) b
WHERE @ids IS NOT NULL
) id, table1 DATA
WHERE FIND_IN_SET(DATA.id, ID._ids)
ORDER BY level, id

原文地址：https://www.cnblogs.com/hl15/p/11145058.html