比如说有四张表A,B,C,D
A
-------------------------
id name
-------------------------
B
-------------------------
id A.id name
-------------------------
C
-------------------------
id B.id name
-------------------------D
-------------------------
id C.id name
-------------------------组合条件就是像网页中选择查询条件一样。
我想请教的事,像这种多表组合条件的查询,SQL语句要怎么写呢。比如说,以A表为主表,条件是D表name=X的记录,应该怎么查呢?
A
-------------------------
id name
-------------------------
B
-------------------------
id A.id name
-------------------------
C
-------------------------
id B.id name
-------------------------D
-------------------------
id C.id name
-------------------------组合条件就是像网页中选择查询条件一样。
我想请教的事,像这种多表组合条件的查询,SQL语句要怎么写呢。比如说,以A表为主表,条件是D表name=X的记录,应该怎么查呢?
from a
where a.id =
(
select a.id
from b
where b.id =
(select b.id
from c
where c.id =
(select c.id
from d
where name =X
)
)
)
select a.*
from a,b,c,d
where d.name = 'x'
and a.id = b.a_id
and b.id = c.b_id
and c.id = d.c_id