SQL实现MYSQL递归查询的方法

现在大家应该都知道mysql版本中已经不支持直接的递归查询了，但是我们可以通过递归到迭代转化的思路是实现树的递归查询，接下来我们就一起去看看SQL实现MYSQL递归查询的方法。

创建表格

CREATE TABLE `treenodes` (
  `id` int , -- 节点ID
  `nodename` varchar (60), -- 节点名称
  `pid` int -- 节点父ID
); 

插入测试数据

INSERT INTO `treenodes` (`id`, `nodename`, `pid`) VALUES
('1','A','0'),('2','B','1'),('3','C','1'),
('4','D','2'),('5','E','2'),('6','F','3'),
('7','G','6'),('8','H','0'),('9','I','8'),
('10','J','8'),('11','K','8'),('12','L','9'),
('13','M','9'),('14','N','12'),('15','O','12'),
('16','P','15'),('17','Q','15'),('18','R','3'),
('19','S','2'),('20','T','6'),('21','U','8');

查询语句

 SELECT id AS ID,pid AS 父ID ,levels AS 父到子之间级数, paths AS 父到子路径 FROM (
   SELECT id,pid,
   @le:= IF (pid = 0 ,0, 
     IF( LOCATE( CONCAT('|',pid,':'),@pathlevel)  > 0 ,   
         SUBSTRING_INDEX( SUBSTRING_INDEX(@pathlevel,CONCAT('|',pid,':'),-1),'|',1) +1
    ,@le+1) ) levels
   , @pathlevel:= CONCAT(@pathlevel,'|',id,':', @le ,'|') pathlevel
   , @pathnodes:= IF( pid =0,',0', 
      CONCAT_WS(',',
      IF( LOCATE( CONCAT('|',pid,':'),@pathall) > 0 , 
        SUBSTRING_INDEX( SUBSTRING_INDEX(@pathall,CONCAT('|',pid,':'),-1),'|',1)
       ,@pathnodes ) ,pid ) )paths
  ,@pathall:=CONCAT(@pathall,'|',id,':', @pathnodes ,'|') pathall 
    FROM treenodes, 
  (SELECT @le:=0,@pathlevel:='', @pathall:='',@pathnodes:='') vv
  ORDER BY pid,id
  ) src
ORDER BY id

最后的结果如下：

??? ID?? 父ID????父到子之间级数? 父到子路径
------?? ?------??? ?--------------------????-------------------?
???? 1?????? 0?????????? ?? 0????????????????? ?? ,0????????????
???? 2?????? 1??????????? ? 1??????????????????? ?,0,1??????????
???? 3?????? 1???????????? ?1?????????????????? ? ,0,1??????????
???? 4?????? 2???????????? ?2???????????????????? ,0,1,2????????
???? 5?????? 2????????????? 2??????????????????? ?,0,1,2????????
???? 6?????? 3????????????? 2?????????????????? ? ,0,1,3????????
???? 7?????? 6??????????? ? 3?????????????????? ? ,0,1,3,6??????
???? 8?????? 0??????????? ? 0??????????????????? ?,0????????????
???? 9?????? 8????????????? 1?????????????????????,0,8??????????
??? 10?????? 8???????????? 1?????????????????????,0,8??????????
??? 11?????? 8??????????? ?1?????????????????? ? ,0,8??????????
??? 12?????? 9??????????? ?2?????????????????????,0,8,9????????
??? 13?????? 9?????????? ? 2??????????????????? ?,0,8,9????????
??? 14????? 12????????? ? 3???????????????????? ?,0,8,9,12?????
??? 15????? 12?????????? ?3??????????????????? ?,0,8,9,12?????
??? 16????? 15????????? ? 4??????????????????? ?,0,8,9,12,15??
??? 17????? 15??????????? 4??????????????????? ?,0,8,9,12,15??
??? 18?????? 3??????????? 2?????????????????? ?? ,0,1,3????????
??? 19?????? 2??????????? 2??????????????????? ? ,0,1,2????????
??? 20?????? 6?????????? ?3??????????????????? ? ,0,1,3,6??????
??? 21?????? 8?????????? ?1??????????????????? ? ,0,8??????

以上就是小编介绍关于SQL实现MYSQL递归查询的方法，希望对大家的学习有所帮助，如果还有疑问，请在本文底部留言吧。

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