Question

我想使用邻接模型（父子密钥）计算在表中维护的任何树结构级别下的所有子节点的数量。表结构和数据如下所示：

id -  item-   parentid    
1  -  A   -   
2  -  B   -   1   
3  -  C   -   1   
4  -  D   -   2   
5  -  E   -   2   
6  -  F   -   3   
7  -  G   -   3   
8  -  H   -   5   
9  -  I   -   5   
10 -  J   -   9   
11 -  K   -   4

例如，B有以下儿童和大孩子结构：

乙
- 电子
  - ħ
  - 我
    - Ĵ
- ˚F
  - ķ

现在，如果您想要计算“B的所有子节点”，我的答案应该是6.

任何基于SQL查询的纯解决方案都会有很大帮助。或者mysql / php也可以。

谢谢！

Answer 1

存储数据的方式不允许使用简单查询来获取总子数。但请看一下：

http://en.wikipedia.org/wiki/Nested_set_model

可以进行这样的查询。

Answer 2

可以使用非递归存储过程相当简单地完成，如下所示：

示例调用

mysql> call category_hier(1);
+--------------+
| num_children |
+--------------+
|            3 |
+--------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

mysql> call category_hier(2);
+--------------+
| num_children |
+--------------+
|            2 |
+--------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

完整脚本

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);


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 tmp on c.parent_cat_id = tmp.cat_id and tmp.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;
*/

select count(*) as num_children from hier where parent_cat_id is not null;

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

end #

delimiter ;

call category_hier(1);

call category_hier(2);

您可以轻松调整此示例以满足您的要求。

希望有所帮助：）

Answer 3

以下是基于PHP的解决方案：

function countChildren($startId) {
    $directDescendents = *_query("SELECT id FROM Table WHERE parentid = ?", array( $startId ));
    $count = *_num_rows($directDescendents);
    while($row = *_fetch_array($directDescendents))
        $count += countChildren($row['id']);
    return $count;
}

$numChildren = countChildren(2); // Number of Children for 'B'

将*_num_rows和*_fetch_array替换为您正在使用的SQL扩展的任何函数。这不如纯SQL解决方案那么高效，但它会起作用。我在函数中查询的方式是假定绑定参数，但是可以根据需要执行查询。

计算表中分层数据的所有子节点

3 个答案: