How does mysql query child nodes
This article will explain in detail how mysql queries child nodes, Xiaobian thinks it is quite practical, so share it with you as a reference, I hope you can gain something after reading this article.
mysql query child node method: first create menu table, and insert data; then use the statement to query, the code is [select id from(select t1.id,if(find_in_set(parent_id, @ pies) > 0......)].
mysql query child node method:
Create menu table:
CREATE TABLE `menu`( `id` int(11) NOT NULL AUTO_INCREMENT COMMENT 'menu id',`parent_id` int(11) DEFAULT NULL COMMENT ' parent nodeid',`menu_name` varchar(128) DEFAULT NULL COMMENT 'menu name',`menu_url` varchar(128) DEFAULT '' COMMENT ' menu path',`status` tinyint(3) DEFAULT '1' COMMENT 'menu status 1-valid; 0-null, PRIMARY KEY (`id`) ENGINE=InnoDB AUTO_INCREMENT=12212 DEFAULT CHARSET=utf8;
Insert data:
INSERT INTO `menu` VALUES ('0 ', null, ' menu0','','1');INSERT INTO `menu` VALUES ('1 ', ' 0','menu1','', ' 1');INSERT INTO `menu` VALUES ('11 ', ' 1','menu11','', ' 1');INSERT INTO `menu` VALUES ('12 ', ' 1','menu12','', ' 1');INSERT INTO `menu` VALUES ('13 ', ' 1','menu13','', ' 1');INSERT INTO `menu` VALUES ('111 ', ' 11','menu111','', ' 1');INSERT INTO `menu` VALUES ('121 ', ' 12','menu121','', ' 1');INSERT INTO `menu` VALUES ('122 ', ' 12','menu122','', ' 1');INSERT INTO `menu` VALUES ('1221 ', ' 122','menu1221','', ' 1');INSERT INTO `menu` VALUES ('1222 ', ' 122','menu1222','', ' 1');INSERT INTO `menu` VALUES ('12211 ', ' 122','menu12211','', ' 1');
The resulting directory structure is shown below:
query
Start with SQL statements:
select id from ( select t1.id, if(find_in_set(parent_id, @pids) > 0, @pids := concat(@pids, ',', id), 0) as ischild from ( select id,parent_id from re_menu t where t.status = 1 order by parent_id, id ) t1, (select @ pies:= id of menu node to query) t2 ) t3 where ischild != 0
For example, if you want to query all child nodes of menu node 12, the result of investigation is:
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