Question

我正在尝试编写带case语句的where子句，该语句将查看@TimeType，然后仅返回这些时间范围之间的行。所以基本上我有3次（早上，下午和晚上）。我在使用之间出现语法错误。 start_time字段是sql time数据类型。这是我到目前为止的内容：

declare @TimeType int

select * from events
where
start_time = case 
when @TimeType = 0 then start_time between '00:00:00' and '11:59:00' 
when @TimeType = 1 then start_time between '12:00:00' and '16:59:00' 
when @TimeType = 2 then start_time between '17:00:00' and '23:59:00' 
end

Answer 1

只需使用常规逻辑：

select e.* 
from events e
where (@TimeType = 0 and start_time between '00:00:00' and '11:59:00') or
      (@TimeType = 1 then start_time between '12:00:00' and '16:59:00') or 
      (@TimeType = 2 then start_time between '17:00:00' and '23:59:00');

通常不建议在case子句中使用where表达式，因为这会阻碍优化器。。。而且可能很难遵循。通常，可以使用基本布尔逻辑来表示相同的逻辑。

Answer 2

您可以在WHERE子句中使用布尔逻辑：

WHERE (@TimeType = 0 AND start_time between '00:00:00' and '11:59:00') OR
      (@TimeType = 1 AND start_time between '12:00:00' and '16:59:00') OR
      (@TimeType = 2 AND start_time between '17:00:00' and '23:59:00')

在BETWEEN中的WHERE子句中使用CASE

2 个答案: