mysql树形结构递归查询

https://www.cnblogs.com/chywx/p/9420726.html

之前一直用的是Oracle，对于树形查询可以使用start with ... connect by 

select * from menu start with id='130000' connect by id = prior parent_id;

 没错，这是Oracle所支持的

现在公司用的是mysql，对于这种查询方式只能通过sql语句实现了

语言都是相通的，何况sql呢

mysql随没有自带的语法支持，不过可以通过创建函数来实现递归查询。

 如下图所示。。。

直接上sql语句

create table `nodelist` (
    `id` int (11),
    `nodecontent` varchar (300),
    `pid` int (11)
); 
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('1','a',NULL);
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('2','b','1');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('3','c','1');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('4','d','2');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('5','e','3');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('6','f','3');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('7','g','5');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('8','h','7');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('9','i','8');
insert into `nodelist` (`id`, `nodecontent`, `pid`) values('10','j','8');

 之后创建一个函数

DROP FUNCTION IF EXISTS `getChild`$$
CREATE DEFINER=`root`@`localhost` FUNCTION `getChild`(rootId INT) RETURNS VARCHAR(1000) CHARSET utf8
BEGIN
        DECLARE ptemp VARCHAR(1000);
        DECLARE ctemp VARCHAR(1000);
               SET ptemp = '#';
               SET ctemp =CAST(rootId AS CHAR);
               WHILE ctemp IS NOT NULL DO
                 SET ptemp = CONCAT(ptemp,',',ctemp);
                SELECT GROUP_CONCAT(id) INTO ctemp FROM nodelist   
                WHERE FIND_IN_SET(pid,ctemp)>0; 
               END WHILE;  
               RETURN ptemp;  
    END$$
DELIMITER ;

OK，查询可以通过将函数当做一个查询条件。

SELECT * FROM nodelist WHERE FIND_IN_SET(id, getChild(3))

上面难度相对比较大，再补充一个简单的自连接查询

SELECT t1.id,t1.nodecontent,t2.nodecontent parentnodecontent FROM nodelist t1
LEFT JOIN nodelist t2
ON t1.pid = t2.id

可以了。

借鉴 https://www.jianshu.com/p/f99665266bb1

里面用到的内置函数 https://baijiahao.baidu.com/s?id=1595349117525189591&wfr=spider&for=pc

你只要能想到的，都有对应的解决方式，幸运的是你该踩得一些坑别人实现给你填好了。

BEGIN
DECLARE sTemp VARCHAR(4000);
DECLARE sTempChd VARCHAR(4000);

SET sTemp = '';
SET sTempChd = cast(cateId as char);

WHILE sTempChd is not NULL DO
if sTemp!='' then
SET sTemp = CONCAT(sTemp,',',sTempChd);
else
SET sTemp = CONCAT('',sTempChd);
end if;

SELECT group_concat(category.id) INTO sTempChd FROM product_front_category AS category where FIND_IN_SET(category.parent_id , sTempChd)>0;
END WHILE;
return sTemp;
END