如何在 SQL Server 中在一次选择中编写多个联合选择

Question

我需要设计一个界面，用户可以选择年份然后月份，年份可能是几年，并且每年可以选择几个月，然后我需要编写一个select语句来检索数据。我可以通过几个选择语句来做到这一点并将它们联合起来。有没有办法一次性写出来？

这个截图显示了我需要设计的界面：

我写的是这样的：

select * 
from yearmonth 
where year = '1390' and month in ('1', '2')
union
select * 
from yearmonth 
where year = '1391' and month in ('3', '4')
union
select * 
from yearmonth 
where year = '1392' and month in ('5')
union
select * 
from yearmonth 
where year = '1393' and month in ('1', '2')

Answer 1

您可以通过将条件与 OR 运算符组合来做到这一点：

select * 
from yearmonth 
where 
  (year = '1390' and month in ('1', '2'))
  or
  (year = '1391' and month in ('3', '4'))
  or
  (year = '1392' and month in ('5'))
  or
  (year = '1393' and month in ('1', '2'))

对于这些条件，代码可以简化为：

select * 
from yearmonth 
where 
  (year in ('1390', '1393') and month in ('1', '2'))
  or
  (year = '1391' and month in ('3', '4'))
  or
  (year = '1392' and month = '5')