发布于 2017-06-12 12:46:52 | 168 次阅读 | 评论: 0 | 来源: 网友投递
Mysql关系型数据库管理系统
MySQL是一个开放源码的小型关联式数据库管理系统，开发者为瑞典MySQL AB公司。MySQL被广泛地应用在Internet上的中小型网站中。由于其体积小、速度快、总体拥有成本低，尤其是开放源码这一特点，许多中小型网站为了降低网站总体拥有成本而选择了MySQL作为网站数据库。
mysql本身不支持递归语法，但可通过自连接变相实现一些简单的递归
--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 |
+------+----------+------+-------+*/