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Home Backend Development PHP Tutorial 问一个联合查询的语句

问一个联合查询的语句

Jun 23, 2016 pm 02:19 PM



如上图所示数据表
怎么读出A中的数据呢?(同时也要读出B中对应的数据)


回复讨论(解决方案)

select * from `a` ,`b`  where  `a`.`bid` like concat('%',`b`.`bid`,'%')

如果要查a表id等于1对应的关联数据,可以写成
select * from `a` ,`b`  where `a`.`id`='1' and `a`.`bid` like concat('%',`b`.`bid`,'%')

是要查a表,结果应该类似这样:

Object{  [id] => 1  [bid] => Object  {     [1] => Object     {        id => 1        content => 'BBBBB'     }     [2] => Object     {        id => 5        content => 'BBBBB'     }     [3] => Object     {        id => 2        content => 'BBBBB'     }  }  conent => 'AAAAA'}
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类似的php伪代码应该是:

foreach ($tablea->result as $a){	echo $a->id	foreach ($a->bid as $b)	{		echo $b.id;		echo $b.content;	}	echo $a.conent}
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打印结果是:

id bid(& b.content) content
------------------------------------
1 1, BBBBBBB AAAAAAAA
1 5, BBBBBBB AAAAAAAA
1 2, BBBBBBB AAAAAAAA
2 2, BBBBBBB AAAAAAAA
2 4, BBBBBBB AAAAAAAA

你要做成这种结果,用程序很容易实现的,上面的SQL其实一定上现实了你的功能

select * from `a` ,`b` where `a`.`bid` like concat('%',`b`.`bid`,'%')

如果要查a表id等于1对应的关联数据,可以写成
select * from `a` ,`b` where `a`.`id`='1' and `a`.`bid` like concat('%',`b`.`bid`,'%')

这是是不是先读b表中的id,然后再模糊查询a表中的bid?

select * from `a` ,`b`  where  `a`.`bid` like concat('%',`b`.`bid`,'%')
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恩,先关联AB表,然后模糊查询a表中的bid是不是在a表的bid中

这样会根据b表的id递增的顺序排序
而不是原先a表中bid逗号字符串的顺序:1,5,2??应该是1-5-2的顺序

建议贴出以下语句以便人家测试
create table ....;

insert into table.... ; 语句

select a.id, b.id as bid, a.content, b.content as bcontent from A表 a, B表 b where find_in_set(b.id, a.bid) order by a.id
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select a.id, b.id as bid, a.content, b.content as bcontent from A表 a, B表 b where find_in_set(b.id, a.bid) order by a.id
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谢谢版主!
find_in_set(b.id, a.bid)好像只能查询到第一条,比如上面的数据表中a.bid是1,5,2,结果只显示b.id=1的那一条!b.id=5, b.id=2的那几条都没查询出来!

你在表B加个冗余字段A_id多好。

CREATE TEMPORARY TABLE a (id int, bid varchar(10), content varchar(10));INSERT INTO a VALUES('1','1,5,2','AAAAAAA');INSERT INTO a VALUES('2','2,4','AAAAAAA');INSERT INTO a VALUES('3','1,3,2','AAAAAAA');CREATE TEMPORARY TABLE b (bid int, content varchar(10));INSERT INTO b VALUES('1','BBBBB');INSERT INTO b VALUES('2','BBBBB');INSERT INTO b VALUES('3','BBBBB');INSERT INTO b VALUES('4','BBBBB');INSERT INTO b VALUES('5','BBBBB');select a.id, b.bid as bid, a.content, b.content as bcontent from a, b where find_in_set(b.bid, a.bid) order by a.id
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原来是我的“1, 5, 2”逗号后面有空格!就没法全查询出来了!空格去掉就ok了

另外,这个find_in_set的查询结果没法按照1-5-2的原始顺序排列!只能按1-2-5递增或5-2-1递减的次序排列啊?

唠叨老大用了另一种更有效率的写法,不过我那些其实也可以得出一样的结果的!
select * from `a` ,`b`  where  `a`.`bid` like concat('%',`b`.`bid`,'%') order by id

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