我想只顯示其中有日期爲空

Question

我想只顯示數據，date是null

這裏說的數據是我的查詢：

$Query = "SELECT att.`EmployeeCode`,emp.FullName ,emp.EmployeeID,emp.Photo,sum(TIME_TO_SEC(att.FinalTime)/60 - IFNULL(sp.TotalTimeLateMark,$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"; 

我怎樣才能做到這一點？

Answer 1

在您的特定情況下，你可能找IS NULL，就像Nilesh製作THAKKAR指出。但HAVING子句中：

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

這是因爲選擇應該發生在連接之後，而不是之前。

Answer 2

您可以使用IS NULL

例如

SELECT * FROM YourTable WHERE DateColumn IS NULL;