我只想显示具有date的数据为null

Question

我只想显示date为null

的数据

这是我的问题：

$Query = "SELECT att.`EmployeeCode`,emp.FullName ,emp.EmployeeID,emp.Photo,sum(TIME_TO_SEC(att.FinalTime)/60 - IFNULL(sp.TotalTimeLateMark,$TotalTimeLateMark))  OverTime
FROM `hr_tblattendancehistory`  att 
left join hr_tblemployee emp on att.EmployeeCode = emp.CardID
left join hr_tblspecialattendancesetting sp on sp.Date = att.Date 
WHERE emp.FullName!='' and att.`Date` Between '$FromDate' and '$Todate=''' and (TIME_TO_SEC(att.FinalTime)/60 -IFNULL(sp.TotalTimeLateMark,$TotalTimeLateMark))  > 0
group by att.`EmployeeCode`,emp.Photo,emp.FullName
order by SUM(TIME_TO_SEC(att.FinalTime)/60 -IFNULL(sp.TotalTimeLateMark,$TotalTimeLateMark))  DESC";

我该怎么做？

Answer 1

您可以使用IS NULL

e.g。

SELECT * FROM YourTable WHERE DateColumn IS NULL;

Answer 2

在您的特定情况下，您可能正在寻找IS NULL，就像Nilesh Thakkar指出的那样。但是在HAVING条款中：

SELECT * FROM YourTable A
LEFT JOIN AnotherTable B on A.DateColumn=B.DateColumn
HAVING DateColumn IS NULL;

这是因为选择应该在加入之后发生，而不是之前。