1. 資料表見文章最後sql
2. 遞迴包含兩個要素：迴圈體，終止條件.net
3. 向上遞迴code
sql：blog
select遞迴
@co as 'code'開發
,( select @co := c.f_code from tree_test c where c.t_code = @co ) as 'f_code'字串
,@lv := @lv - 1 as 'level'get
fromclass
tree_test a ,( select @lv := b.t_level, @co := b.t_code from tree_test b where b.t_code = '300101') as xtest
where @lv > 0
分析：迴圈體： select @co := c.f_code from tree_test c where c.t_code = @co
以每次查詢的父級**做為下次查詢得分類**條件，一層層往上查詢
終止條件：層級，@lv 當查詢到頂級的實時結束查詢
4. 向下遞迴
sql：
select
@co as 'code'
,( select @co := group_concat(c.t_code)from tree_test c where find_in_set(c.f_code,@co)) as 'f_code'
from
tree_test a ,( select @co := group_concat(b.t_code) from tree_test b where b.t_code = '10') as x
where @co is not null
分析：迴圈體： select @co := group_concat(c.t_code)from tree_test c where find_in_set(c.f_code,@co) 以每次查詢的下級**集合做為下次查詢得分類**條件，一層層往下查詢，這裡用到了 分組合併字串group_concat()以及字串級查詢find_in_set()
終止條件：當沒有找到下級的資訊時，便可認為查詢完畢
5. myql 定義變數賦值 @param := 10
(以上僅作技術研究，實際開發中避免複雜sql)
樹級表：
create table `tree_test` (
`t_id` int(11) not null auto_increment comment '自增id',
`t_code` int(11) not null comment '節點**',
`t_name` varchar(200) default null comment '節點名稱',
`f_code` int(11) not null default '0' comment '父級節點',
`t_level` int(1) not null default '1' comment '節點層級',
primary key (`t_id`)
) engine=innodb auto_increment=15 default charset=utf8;
資料：insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('2', '10', '一級節點_1', '0', '1');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('3', '20', '一級節點_2', '0', '1');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('4', '30', '一級節點_3', '0', '1');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('5', '1001', '二級節點_1_1', '10', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('6', '1002', '二級節點_1_2', '10', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('7', '1003', '二級節點_1_3', '10', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('8', '2001', '二級節點_2_1', '20', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('9', '2002', '二級節點_2_2', '20', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('10', '3001', '二級節點_3_1', '30', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('11', '3002', '二級節點_3_2', '30', '2');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('12', '100201', '**節點_1_2_1', '1002', '3');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('13', '100202', '**節點_1_2_2', '1002', '3');
insert into `tree_test` (`t_id`, `t_code`, `t_name`, `f_code`, `t_level`) values ('14', '300101', '**節點_3_1_2', '3001', '3');
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