子句没有按预期工作

Question

我有以下语句

select pkid 
from AttendancePosting 
where datename(dw,AttDate) = 'Sunday' and empid=4 and attdate='2015-12-13' 
group by PKId,timeout
--having 9=9
having cast(sum((datepart(minute, timeout)))/2 as float )+''=cast(datepart(minute,timeout) as float) +''

问题是

having cast(sum((datepart(minute, timeout)))/2 as float )+''=cast(datepart(minute,timeout) as float) +''

不起作用。cast(sum((datepart(minute, timeout)))/2 as float )和cast(datepart(minute,timeout) as float)都带来了相同的值，但select语句仍然没有获取任何记录，都返回9

我已经像这个一样检查过了

select pkid 
from AttendancePosting 
where datename(dw,AttDate) = 'Sunday' and empid=4 and attdate='2015-12-13' 
group by PKId,timeout
having 9=9

它带来了记录，任何帮助都将不胜感激。

Answer 1

首先，您的语句datepart(minute, timeout)/2将返回一个整数。通过像datepart(minute, timeout)/2.这样更加精确，可以使SQL Server变得更加精确。

其次，浮点数是一种近似值。您最好使用ROUND()，并指定您认为合适的小数位数。例如：round(sum((datepart(minute, timeout)))/2.0, 3)。