嗨,好几天以来,我一直在MySQL中解决这个问题,但是我无法弄清楚。你们有什么建议吗?
基本上,我有一个类别表,其域如:id,name(类别名称)和parent(类别的父代ID)。
id
name
parent
示例数据:
1 Fruit 0 2 Apple 1 3 pear 1 4 FujiApple 2 5 AusApple 2 6 SydneyAPPLE 5 ....
有许多级别,可能超过3个级别。我想创建一个根据层次结构将数据分组的sql查询:父级>子级>孙子级>等。
它应该输出树结构,如下所示:
1 Fruit 0 ^ 2 Apple 1 ^ 4 FujiApple 2 - 5 AusApple 2 ^ 6 SydneyApple 5 - 3 pear 1
我可以使用一个SQL查询吗?我尝试并起作用的替代方法如下:
SELECT * FROM category WHERE parent=0
此后,我再次遍历数据,然后选择parent = id所在的行。这似乎是一个糟糕的解决方案。因为它是mySQL,所以不能使用CTE。
如果使用存储过程,则可以在一次从php到mysql的调用中完成:
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) $sql = sprintf("call category_hier(%d)", $id);
希望这可以帮助 :)
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), ('USA',1), ('Illinois',2), ('Chicago',2), ('Color',null), ('Black',3), ('Red',3);
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; /* http://dev.mysql.com/doc/refman/5.0/en/temporary-table-problems.html */ create temporary table tmp engine=memory select * from hier; while not v_done do if exists( select 1 from categories p inner join hier on p.parent_cat_id = hier.cat_id and hier.depth = v_depth) then insert into hier select p.parent_cat_id, p.cat_id, v_depth + 1 from categories p inner join tmp on p.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 p.cat_id, p.name as category_name, b.cat_id as parent_cat_id, b.name as parent_category_name, hier.depth from hier inner join categories p on hier.cat_id = p.cat_id left outer join categories b on hier.parent_cat_id = b.cat_id order by hier.depth, hier.cat_id; drop temporary table if exists hier; drop temporary table if exists tmp; end #
delimiter ; call category_hier(1); call category_hier(2);
drop table if exists geoplanet_places; create table geoplanet_places ( woe_id int unsigned not null, iso_code varchar(3) not null, name varchar(255) not null, lang varchar(8) not null, place_type varchar(32) not null, parent_woe_id int unsigned not null, primary key (woe_id), key (parent_woe_id) ) engine=innodb; mysql> select count(*) from geoplanet_places; +----------+ | count(*) | +----------+ | 5653967 | +----------+
所以表中有560万行(位置),让我们看看从php调用的邻接表实现/存储过程是如何处理的。
1 records fetched with max depth 0 in 0.001921 secs 250 records fetched with max depth 1 in 0.004883 secs 515 records fetched with max depth 1 in 0.006552 secs 822 records fetched with max depth 1 in 0.009568 secs 918 records fetched with max depth 1 in 0.009689 secs 1346 records fetched with max depth 1 in 0.040453 secs 5901 records fetched with max depth 2 in 0.219246 secs 6817 records fetched with max depth 1 in 0.152841 secs 8621 records fetched with max depth 3 in 0.096665 secs 18098 records fetched with max depth 3 in 0.580223 secs 238007 records fetched with max depth 4 in 2.003213 secs
总的来说,我对那些寒冷的运行时感到非常满意,因为我什至不会开始考虑将数万行数据返回到我的前端,而是宁愿动态地构建树,每次调用只获取几个级别。哦,以防万一您以为innodb比myisam慢- 我测试的myisam实现在所有方面都慢了一倍。
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