select a_id from a where a_name='t'
查询结果a_id='A1'select b_id from b where a_id='A1'
查询结果b_id='B2'select c_id from c where b_id='B2'
查询结果c_id='c3'select * from c where c_id='c3'
.....
条件查询第1个表a,然后用a表的结果(a_id='A1')去查询b表。
再用b表的结果(b_id='B2')去查询c表。
再用c表的结果(结果c_id='c3')去查询d表。
a->b->c-d有没什么办法简化的。用一条语句就可以完成?做视图?
查询结果a_id='A1'select b_id from b where a_id='A1'
查询结果b_id='B2'select c_id from c where b_id='B2'
查询结果c_id='c3'select * from c where c_id='c3'
.....
条件查询第1个表a,然后用a表的结果(a_id='A1')去查询b表。
再用b表的结果(b_id='B2')去查询c表。
再用c表的结果(结果c_id='c3')去查询d表。
a->b->c-d有没什么办法简化的。用一条语句就可以完成?做视图?
from a, b, c
where a.a_id = b.a_id
and b.b_id = c.b_id
and a.a_name = 't'
查询结果a_id='A1'select b_id from b where a_id='A1'
查询结果b_id='B2'select c_id from c where b_id='B2'
查询结果c_id='c3'select * from c where c_id='c3'
select c.* from a,b,c
where a.a_id=b.a_id and b.b_id=c.b_id and a.name='t'
--a_name看错了 写成a.name
select c.* from a,b,c
where a.a_id=b.a_id and b.b_id=c.b_id and a_name='t'
(select c_id from c where b_id=
(select b_id from b where a_id=
(select a_id from a where a_name='t')));