MySQL之遞歸小問題。本站提示廣大學習愛好者:(MySQL之遞歸小問題)文章只能為提供參考,不一定能成為您想要的結果。以下是MySQL之遞歸小問題正文
投稿:mdxy-dxy
這篇文章主要介紹了MySQL之遞歸小問題,需要的朋友可以參考下mysql本身不支持遞歸語法,但可通過自連接變相實現一些簡單的遞歸
--遞歸小方法:臨時表和普通表的不同方法 --這題使用的是2次臨時表查詢父節點的遞歸 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', '大學教師', '37e2ea0a-1c31-3412-455a-5e60b8395f7d' union all select '1ce203ac-ee34-b902-6c10-c806f0f52876','小學教師', '37e2ea0a-1c31-3412-455a-5e60b8395f7d' union all select '37e2ea0a-1c31-3412-455a-5e60b8395f7d', '教師' , null union all select 'c877b7ea-4ed3-f472-9527-53e1618cb1dc', '高數老師', '13ed38f1-3c24-dd81-492f-673686dff0f3' union all select 'ce50a471-2955-00fa-2fb7-198f6b45b1bd', '中學教師', '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 | 大學教師 | 37e2ea0a-1c31-3412-455a-5e60b8395f7d | | 37e2ea0a-1c31-3412-455a-5e60b8395f7d | 教師 | NULL | +--------------------------------------+----------+--------------------------------------+ call usp_ser('13ed38f1-3c24-dd81-492f-673686dff0f3'); +--------------------------------------+------+----------+ | id | name | parentid | +--------------------------------------+------+----------+ | 37e2ea0a-1c31-3412-455a-5e60b8395f7d | 教師 | NULL | +--------------------------------------+------+----------+ call usp_ser('37e2ea0a-1c31-3412-455a-5e60b8395f7d'); Empty set (0.02 sec)
上面的方法因為由於MySQL中不允許在同一語句中對臨時表多次引用,所以用2次臨時表
下面給個一次性用普通表完成的 查詢子節點的遞歸查詢
核心代碼
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 | +------+----------+------+-------+*/