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  • mysql 递归查找所有子节点

    1 select dept_id from (
    2               select t1.dept_id,t1.parent_id,
    3               if(find_in_set(parent_id, @pids) > 0, @pids := concat(@pids, ',', dept_id), 0) as ischild
    4               from (
    5                    select dept_id,parent_id from sys_dept t where t.del_flag = '0' order by parent_id, dept_id
    6                   ) t1,
    7                   (select @pids := 要查询的节点id) t2
    8              ) t3 where ischild != 0;

    解释:

    @pids := 要查询的节点id   变量定义。
    concat()  拼接字符串
    find_in_set(parent_id, @pids)  parent_id 字符串是否在@pids字符串中。
      select find_in_set('2','1,2');返回2
      select find_in_set('6','1');返回0

    if(express1,express2,express3)条件语句,if语句类似三目运算符,当exprss1成立时,执行express2,否则执行express3;
    拆分语句:select dept_id,parent_id from sys_dept t where t.del_flag = '0' order by parent_id, dept_id
    select @pids := 要查询的节点id

    select * from (
    select dept_id,parent_id from sys_dept t where t.del_flag = '0' order by parent_id, dept_id
    ) t1,
    (select @pids :=4) t2

    select t1.dept_id,t1.parent_id,t2.*,
    if(find_in_set(parent_id, @pids) > 0, @pids := concat(@pids, ',', dept_id), 0) as ischild
    from (
    select dept_id,parent_id from sys_dept t where t.del_flag = '0' order by parent_id, dept_id
    ) t1,
    (select @pids := 4) t2

    select dept_id from (
    select t1.dept_id,t1.parent_id,t2.*,
    if(find_in_set(parent_id, @pids) > 0, @pids := concat(@pids, ',', dept_id), 0) as ischild
    from (
    select dept_id,parent_id from sys_dept t where t.del_flag = '0' order by parent_id, dept_id
    ) t1,
    (select @pids := 4) t2
    ) t3 where ischild != 0;

     
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  • 原文地址:https://www.cnblogs.com/bulrush/p/12015504.html
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