mysql 递归查询树形目录

早些时候看到一篇《一句SQL实现MYSQL的递归查询》，但是必须是在 id大于pid 的情况下才能使用。

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       

改了一下，没有这个限制，ssid应该也能使用。

  SELECT *, 
         @Pn:=pid, 
         @path:=(
             SELECT GROUP_CONCAT(
                        SUBSTRING_INDEX( 
                        @Pn:= (SELECT CONCAT(pid,'|',nodename) FROM treenodes WHERE id=SUBSTRING_INDEX(@Pn,'|',1)),
                        '|',
                        -1 ) 
                    ORDER BY id DESC SEPARATOR '-' )
             FROM treenodes WHERE @Pn IS NOT NULL ORDER BY id ASC ) 
         AS path,
         LENGTH (@path) - LENGTH (REPLACE(@path, '-', ''))+1 AS lv
  FROM treenodes;

 

 结果如下