在一条select语句中的不同条件

Question

你怎么能Select两列，并且每列都测试它自己的条件而不是其他条件？

比方说，我有一个选择Count表中的每个记录。在一个专栏中，我希望从本周开始记录每一条记录，而在第二个专栏中，我希望自今年年初以来的所有记录。

我有两个条件，但它们都适用于特定的列：

 WHERE date BETWEEN @Monday AND @SUNDAY /* Weekly */ 
     WHERE date >= @JanuaryFirst    /* Annual */ 

但不能只是把它喜欢这样，因为我只在两列获得本周的纪录。我认为我可以使用IF的条件，但我不认为我可以简单地说“如果你是专栏A测试，如果不测试第二个”。

Answer 1

内在地运用进行选择，这样的：

select vehicule, 
     (select count(*) from tablename t1 where t1.vehicule = t.vehicule and date BETWEEN @Monday AND @SUNDAY) as 'Weekly', 
     (select count(*) from tablename t1 where t1.vehicule = t.vehicule and date >= @JanuaryFirst) as 'Annual' 
from tablename t 

Answer 2

如果你想避免子查询，你可以使用：

select vehicule, 
sum(case when date BETWEEN @Monday AND @SUNDAY then 1 else 0 end) as 'Weekly', 
sum(case when date >= @JanuaryFirst then 1 else 0 end) as 'Annual' 
group by vehicule 

Answer 3

这里是一个版本，不会产生多扫描：

select vehicule, 
    weekly = SUM(CASE WHEN date BETWEEN @Monday AND @SUNDAY THEN 1 ELSE 0 END), 
    annual = SUM(CASE WHEN date >= @JanuaryFirst THEN 1 ELSE 0 END) 
from dbo.tablename AS t 
GROUP BY vehicule; 

或者你也可以尝试稍微不详细：

select vehicule, 
    weekly = COUNT(CASE WHEN date BETWEEN @Monday AND @SUNDAY THEN 1 END), 
    annual = COUNT(CASE WHEN date >= @JanuaryFirst THEN 1 END) 
from dbo.tablename AS t 
GROUP BY vehicule;