MySQL之递归小问题案例分享

--递归小方法：临时表和普通表的不同方法
--这题使用的是2次临时表查询父节点的递归 
drop table if exists test;
create table test(
id varchar(100),
name varchar(20),
parentid varchar(100)
);
insert test select
'13ed38f1-3c24-dd81-492f-673686dff0f3', '大学教师', '37e2ea0a-1c31-3412-455a-5e60b8395f7d' union all select 
'1ce203ac-ee34-b902-6c10-c806f0f52876','小学教师', '37e2ea0a-1c31-3412-455a-5e60b8395f7d' union all select 
'37e2ea0a-1c31-3412-455a-5e60b8395f7d', '教师' ,      null                union all select 
'c877b7ea-4ed3-f472-9527-53e1618cb1dc', '高数老师', '13ed38f1-3c24-dd81-492f-673686dff0f3' union all select 
'ce50a471-2955-00fa-2fb7-198f6b45b1bd', '中学教师', '37e2ea0a-1c31-3412-455a-5e60b8395f7d';
 
delimiter $$
 
create procedure usp_ser(in idd varchar(100))
begin
declare lev int;
set lev=1;
drop table if exists tmp1;
drop table if exists tmp2;
CREATE TEMPORARY TABLE tmp1(id varchar(100),name varchar(20),parentid varchar(100),levv int);
CREATE TEMPORARY TABLE tmp2(pid varchar(100));
insert tmp2 select parentid from test where id=idd;
insert tmp1 select t.* , lev from test t join tmp2 a on t.id=a.pid;
    while exists(select 1 from tmp2 )
do
truncate tmp2;
set lev=lev+1;
insert tmp2 select t.id from test t join tmp1 a on t.id=a.parentid and a.levv=lev-1;
insert tmp1 select t.*,lev from test t join tmp2 a on t.id=a.pid;
end while ;
select id,name,parentid from tmp1;
end;
$$
 
delimiter ;
 
 call usp_ser('c877b7ea-4ed3-f472-9527-53e1618cb1dc');
+--------------------------------------+----------+--------------------------------------+
  id                    name     parentid                
+--------------------------------------+----------+--------------------------------------+
  13ed38f1-3c24-dd81-492f-673686dff0f3   大学教师   37e2ea0a-1c31-3412-455a-5e60b8395f7d  
  37e2ea0a-1c31-3412-455a-5e60b8395f7d   教师     NULL                  
+--------------------------------------+----------+--------------------------------------+
 
 call usp_ser('13ed38f1-3c24-dd81-492f-673686dff0f3');
+--------------------------------------+------+----------+
  id                    name   parentid  
+--------------------------------------+------+----------+
  37e2ea0a-1c31-3412-455a-5e60b8395f7d   教师   NULL    
+--------------------------------------+------+----------+
 
 call usp_ser('37e2ea0a-1c31-3412-455a-5e60b8395f7d');
 
Empty set (0.02 sec)

上面的方法因为由于MySQL中不允许在同一语句中对临时表多次引用，所以用2次临时表
下面给个一次性用普通表完成的 查询子节点的递归查询

核心代码

drop table if exists test;
create table test(
id INT,
parentid INT
);
insert test select
1, 0 UNION ALL SELECT 
2, 1 UNION ALL SELECT 
3, 1 UNION ALL SELECT 
4, 0 UNION ALL SELECT 
5, 2 UNION ALL SELECT 
6, 5 UNION ALL SELECT 
7, 3 ;
Go
 
delimiter $$
 
create procedure usp_ser(in idd varchar(100))
begin
declare lev int;
set lev=1;
drop table if exists tmp1;
CREATE TABLE tmp1(id INT,parentid INT ,levv INT,ppath VARCHAR(1000));

INSERT tmp1 SELECT *,lev,id FROM test WHERE parentid=idd;

 while row_count()>0
do

set lev=lev+1;
insert tmp1 select t.*,lev,concat(a.ppath,t.id) from test t join tmp1 a on t.parentid=a.id AND levv=LEV-1;
 
end while ;
SELECT * FROM tmp1;
 
end;
$$
 
delimiter ;
 
 call usp_ser(0);
 
/*
+------+----------+------+-------+
  id    parentid   levv   ppath  
+------+----------+------+-------+
   1      0    1   1    
   4      0    1   4    
   2      1    2   12   
   3      1    2   13   
   5      2    3   125   
   7      3    3   137   
   6      5    4   1256  
+------+----------+------+-------+*/

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