100分求一SQL，希望大家给点支持！！！在线等~~~~~~~~~~~

[daboby]

有主表a，从表b，c
连接条件是a.ID_b=b.id,a.ID_c=c.id
要求查询出b.value,c.value
2个外连接的查询

[marco08]

select * from a
left join b on a.ID_b=b.id
left join c on a.ID_c=c.id

[gc_ding]

select b.value,c.value
from a,b,c
where a.ID_b=b.id and a.ID_c=c.id

[daboby]

要求查询出b.value,c.value

[allright_flash]

select b.value,c.value from a
left join b on a.ID_b=b.id
left join c on a.ID_c=c.id

[allright_flash]

select b.value,c.value
from a,b,c
where a.ID_b=b.id and a.ID_c=c.id

[dawugui]

select b.value,c.value
from a,b,c
where a.ID_b=b.id and a.ID_c=c.id

[liubeiru_1982]

都正确,但是要注意 笛卡尔积的产生

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[rfq]

select b.value,c.value from a
left join b on a.ID_b=b.id
left join c on a.ID_c=c.id

[splory]

看来问题解决了
那就顶一下

[daboby]

按我的需要，如果a表有100条记录，查询出来的结果应该也是100条记录。
因为a是主表，我只是显示其中的2个字段内容。

[daboby]

都正确,但是要注意 笛卡尔积的产生



不知道有没有这个问题

[daboby]

不好意思，题目有点差别，大家在帮忙看看~

有主表a，从表b，c,b有从表d
连接条件是a.ID_b=b.id, b.ID_d=d.id,a.ID_c=c.id
要求查询出d.value,c.value
2个外连接的查询

[子陌红尘]

SELECT
B.value,C.value
FROM
表a A
LEFT JOIN
(SELECT M.id,N.value FROM 表b M LEFT JOIN 表d N ON M.ID_d=N.id) B
ON
A.ID_b=B.id
LEFT JOIN
表c C
ON
A.ID_c=C.id

[penglewen]

select b.value,c.value
from a,b,c
where a.ID_b=b.id and a.ID_c=c.id

[JACKYANQUN]

a是主表,b,c是从表
要是a表中的资料要全部显示的话就
select * from a
left join b on a.ID_b=b.id
left join c on a.ID_c=c.id

如果不要求全部显示a表资料的话就内连接

select b.value,c.value
from a,b,c
where a.ID_b=b.id and a.ID_c=c.id

[lovelizheng]

select b.value,c.value from a
inner join b on a.id_b = b.id
inner join c on a.id_c = c.id

[中国风]

a.ID_b=b.id,a.ID_c=c.id
left join 用 以a表的全部数据为基础连接b、c表
这样如a.id是a表是唯一的，但在b表有两条记录，统计结果会多出一条记录。
连接c表同样。只有b_id和c.id是唯一的。统计结果才会正确

[daboby]

libin_ftsafe(子陌红尘：当libin告别ftsafe) ( )
SELECT
B.value,C.value
FROM
表a A
LEFT JOIN
(SELECT M.id,N.value FROM 表b M LEFT JOIN 表d N ON M.ID_d=N.id) B
ON
A.ID_b=B.id
LEFT JOIN
表c C
ON
A.ID_c=C.id


-------------------
感觉是符合要求的
试了一下，老是报错
单个left join ...on结果都是对的
但是整个语句会报错
好像不能2个left join ...on一起用

[daboby]

错误信息：Error of syntax (operator absent) in the expression ' A.id_b=B.id left join 表c C on A.id_c=C.id'

[liubeiru_1982]

试验一下这个
select d.value,c.value from b,d,a,c
where (d.id in (select b.id_d from a,b where a.ID_b=b.id))
and (c.id in (select a.ID_c from a,c where a.ID_c=c.id))



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