若是用php程序查询的话,要用递归屡次查询数据库,很慢,也增长了服务器的压力,后来发现用一句sql就能直接返回全部的父级或子级php
用户表sql
t_id | parent_id 1 | 0 2 | 1 3 | 0 4 | 2 5 | 4
sql语句 查找全部父级(包含自己)数据库
SELECT T2.t_id FROM ( SELECT @r AS _id, (SELECT @r := parent_id FROM t_user WHERE t_id = _id) AS parent_id, @l := @l + 1 AS lvl FROM (SELECT @r := 5, @l := 0) vars, t_user h WHERE @r <> 0 AND parent_id > 0 ) T1 JOIN t_user T2 ON T1._id = T2.t_id ORDER BY T1.lvl DESC
筛选结果服务器
|t_id| |1 | |2 | |4 | |5 |
sql语句 查找全部子级(不包含自己).net
SELECT t_id FROM ( SELECT * FROM t_user where parent_id > 0 ORDER BY parent_id, t_id DESC ) realname_sorted, (SELECT @pv :=1) initialisation WHERE (FIND_IN_SET(parent_id,@pv)>0 And @pv := concat(@pv, ',', t_id))
筛选结果code
|t_id| |2 | |4 | |5 |
查找子级是同事写的,查找父级是本身写的,记下来方便之后用blog
根据一级节点查找对应的二级子节点数量递归
SELECT t_id, ( SELECT count(a.parent_id) FROM t_user a WHERE a.parent_id = b.t_id) count FROM t_user b WHERE b.parent_id = 0
筛选结果it
|t_id|count |1 | 1 |3 | 0
http://blog.csdn.net/itchiang/article/details/9270245