类别和子类别的递归函数 [英] Recursive function for category and sub-category

问题描述

我需要有关递归函数的帮助.我们有一个类别表，其中包含category_id，category_name和parent_id:

I need help regarding recursive function We have a category table contains category_id,category_name and parent_id:

category_id  category_name  parent_id
------------+--------------+----------
1 Agriculture 0 
2 Appearl & Fashion 0 
3 Chemicalas 0 
4 Plastic & Plastic Products 0 
5 Automobile 0 
14 Coconut Shell Products 1 
15 Nuts & Kernels 1 
16 Plant & Animal Oil 1 
17 Potpourri 1 
18 Raw Cotton & Cotton Waste 1 
19 Rice 1 
20 Tea 1 
21 Seeds 1 
22 Vegetable 1 
23 White Rice 19 
24 Green Rice 19 
25 Basmati Rice 19 
26 Boiled Rice 19 
27 Fresh Preserved Vegetables 22 
28 Frozen & Dried Vegetables 22 
29 Others 22 
30 Activated Carbon 3 

我们希望使用递归函数输出以下类别:

We want the output of the category like below using recursive function:

Agriculture > Rice > White rice  
Agruculture > Rice > Basmati rice

pls.指导并帮助我

pls. guide and help me

推荐答案

使用非递归/邻接列表存储过程实现，从PHP到MySQL的单个调用中非常简单.

Fairly simple to do in a single call from PHP to MySQL using a non-recursive/adjacency list stored procedure implementation.

希望它会有所帮助:)

示例通话

mysql> call category_hier(1);
+--------+---------------+---------------+----------------------+-------+
| cat_id | category_name | parent_cat_id | parent_category_name | depth |
+--------+---------------+---------------+----------------------+-------+
|      1 | Location      |          NULL | NULL                 |     0 |
|      3 | USA           |             1 | Location             |     1 |
|      4 | Illinois      |             3 | USA                  |     2 |
|      5 | Chicago       |             3 | USA                  |     2 |
+--------+---------------+---------------+----------------------+-------+
4 rows in set (0.00 sec)

mysql> call category_hier(2);
+--------+---------------+---------------+----------------------+-------+
| cat_id | category_name | parent_cat_id | parent_category_name | depth |
+--------+---------------+---------------+----------------------+-------+
|      2 | Color         |          NULL | NULL                 |     0 |
|      6 | Black         |             2 | Color                |     1 |
|      7 | Red           |             2 | Color                |     1 |
+--------+---------------+---------------+----------------------+-------+
3 rows in set (0.00 sec)


$sqlCmd = sprintf("call category_hier(%d);", 1);
$sqlCmd = sprintf("call category_hier(%d);", 2);

表格和测试数据

drop table if exists categories;
create table categories
(
cat_id smallint unsigned not null auto_increment primary key,
name varchar(255) not null,
parent_cat_id smallint unsigned null,
key (parent_cat_id)
)
engine = innodb;

insert into categories (name, parent_cat_id) values
('Location',null), 
('Color',null), 
   ('USA',1), 
      ('Illinois',3), 
      ('Chicago',3), 
   ('Black',2), 
   ('Red',2);

存储过程

drop procedure if exists category_hier;

delimiter #

create procedure category_hier
(
in p_cat_id smallint unsigned
)
begin

declare v_done tinyint unsigned default 0;
declare v_depth smallint unsigned default 0;

create temporary table hier(
 parent_cat_id smallint unsigned, 
 cat_id smallint unsigned, 
 depth smallint unsigned default 0
)engine = memory;

insert into hier select parent_cat_id, cat_id, v_depth from categories where cat_id = p_cat_id;
create temporary table tmp engine=memory select * from hier;

/* http://dev.mysql.com/doc/refman/5.0/en/temporary-table-problems.html */

while not v_done do

    if exists( select 1 from categories c
        inner join hier on c.parent_cat_id = hier.cat_id and hier.depth = v_depth) then

        insert into hier select c.parent_cat_id, c.cat_id, v_depth + 1 from categories c
            inner join tmp on c.parent_cat_id = tmp.cat_id and tmp.depth = v_depth;

        set v_depth = v_depth + 1;          

        truncate table tmp;
        insert into tmp select * from hier where depth = v_depth;

    else
        set v_done = 1;
    end if;

end while;

select 
 c.cat_id,
 c.name as category_name,
 p.cat_id as parent_cat_id,
 p.name as parent_category_name,
 hier.depth
from 
 hier
inner join categories c on hier.cat_id = c.cat_id
left outer join categories p on hier.parent_cat_id = p.cat_id
order by
 hier.depth;

drop temporary table if exists hier;
drop temporary table if exists tmp;

end #

delimiter ;

这篇关于类别和子类别的递归函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！