Question

我有表A，表B和表C.

我想从表A中选择2个字段，从表B中选择一个字段（我假设这两个字段之间是内连接），并在表C中找到表B上标识符的每个记录的计数。

所以我会：

OpeartiveId | OperativeNumber | JobLocation | CountOfJobIdInWorkTable

编辑：

Operative
OperativeId
OperativeNumber

Jobs
JobId
JobLocation

Work
JobId
OperativeId

Answer 1

假设您还希望a和b中的记录在c中没有匹配记录，则需要外部联接：

select a.pk_a, b.pk_b, count(c.pk_c) 
from a 
inner join b on a.pk_a = b.pk_a 
left outer join c on b.pk_b = c.pk_b 
group by a.pk_a, b.pk_b;

Answer 2

将其翻译成您的实际架构并尝试：

select a.one, a.two, b.three, count(c.id)
from a
join b on a.id=b.id
left join c on c.bid=b.id
group by a.one, a.two, b.three, b.id

Answer 3

不确定这是否是您要找的。看着你提供的文件，我想出了这个。

select o.operativeId, o.OperativeNumber, j.JobLocation, COUNT(w.jobId)
from dbo.Operative o
Inner join works w
    ON o.OperativeID = w.OperativeId
INNER JOIN jobs j
ON w.jobId = j.jobId
GROUP by o.operativeId, o.OperativeNumber, j.JobLocation

Answer 4

select a.a,a.b,b.a,(select count(*) from c where c.b_id = b.id)
from a 
join b on a.b_id = b.id

基本连接和聚合？

4 个答案: