运算符T-SQL除外

Question

任务：为在任何2个月内至少购买1次但未在所有3个月内购买的客户显示c_id和c_name。

First Month = November
Second Month = December
Third Month = January



SELECT c_id, c_name
FROM books
WHERE MONTH(order_date) = 11
INTERSECT
SELECT c_id, c_name 
FROM books
WHERE MONTH(order_date) = 12
EXCEPT
SELECT c_id, c_name
FROM books
WHERE MONTH(order_date) = 1

我现在的代码否定了第3个月，但它没有满足任务所要求的，可以互换选择任何2个月。

规则是：无计数，无子查询，无加入

Answer 1

我设法想出了这个。

select c_id,c_name from books where month(order_date) = 1
intersect 
select c_id,c_name from books where month(order_date) = 11
union
select c_id,c_name from books where month(order_date) = 1
intersect 
select c_id,c_name from books where month(order_date) = 12
union
select c_id,c_name from books where month(order_date) = 12
intersect 
select c_id,c_name from books where month(order_date) = 11
except
select c_id,c_name from books where month(order_date) = 1
intersect 
select c_id,c_name from books where month(order_date) = 11
intersect 
select c_id,c_name from books where month(order_date) = 12

这相当于表达式：

(Set A intersect Set B) union (Set A intersect Set C) union (Set C intersect Set B) minus (Set A intersect Set B intersect Set C)，

或正如您在image中看到的那样，区域AB，AC和BC

这当然不优雅，但考虑到要求，蛮力似乎是一种有效的方法。