Question

我想两次检索相同的列，但条件不同。

我的查询是这样的，但是以下查询检索了两个不同的列。但是我想两次获得同一列，如何实现呢？

Select name from tbCustomer where ID in (select ID from tbOldCustomer where oldID= 1)
Select name from tbCustomer where ID in (select ID from tbOldCustomer where oldID= 2)

tbCustomer 有两列：
ID 名称
1 aaa
2 bbb
3 ccc
4 ddd

tbOldCustomer 有两列：

ID 旧ID
1 2
2 1
3 1
4 2
4 1

想获取（1，2）中oldID的名称，输出应为以下内容：

名称 名称1
bbb aaa
ccc ddd
ddd

Answer 1

使用存在

select t1.name 
from tbCustomer t1 
exists( select 1 from  tbOldCustomer t2  where  t1.id = t2.id
                                       and t2.oldid in (1,2)
        )

Answer 2

我认为您可以仅使用JOIN

Select name 
from tbCustomer tc 
inner join tbOldCustomer toc On toc.id = tc.id
where toc.oldID IN (1,2)

Answer 3

您可以尝试将conditional aggregation与case when expression一起使用

select max(case when oldID= 1 then name end) as name1,
       max(case when oldID= 2 then name end) as name2
from tbCustomer join tbOldCustomer on ID=oldID where oldid in (1,2)
group by oldid

Answer 4

您必须尝试

Select tc.name, toc.name from tbCustomer tc inner join 
tbOldCustomer toc On toc.id = c.id where toc.oldID IN (1,2)

Answer 5

请尝试这个。

Select name from tbCustomer where ID in (select ID from tbOldCustomer where oldID IN(1,2))

OR

Select A.name from tbCustomer A
INNER JOIN tbOldCustomer  B
ON A.id = B.Id
AND B.OldId In (1,2)

Answer 6

尝试一下

SELECT  name 
FROM tbCustomer tb1 
JOIN (SELECT ID FROM tbOldCustomer WHERE oldID = 1 OR oldID= 2) tb2
     ON tb1.ID = tb2.ID
WHERE tb1.ID IN (SELCT ID from tbOldCustomer where oldID in (1, 2))

在SQL中使用不同条件两次获取同一列

6 个答案: