SQL查询 - 某种选择不同？

Question

假设我有特定日期的客户记录，例如：

Cs  day
--  ---
01  Tue
02  Tue
03  Wed
01  Wed
04  Thu
02  Thu

我需要一个只返回周二和周三两个客户的＃的查询。在这种情况下，只有Cs＃01。

Answer 1

select distinct c1.Cs
from Customers c1 
inner join Customers c2 on c2.Cs=c1.Cs
where c2.day='Tue' and c1.day='Wed'

Answer 2

使用子查询...

Select distinct cs From Customers
Where Exists (Select * from Customers
              Where day = 'Tue')
  And Exists (Select * from Customers
              Where day = 'Wed')