選擇查詢案例問題

Question

SELECT * 
CASE 
    WHEN (Employees.End_Date is null) 
THEN select 
     EmpId, 
     Emp_Name, 
     Salary , 
     Start_date , 
     End_dat , 
     DATEDIFF(DATE_ADD(Start_Date, INTERVAL 30 DAY), Start_Date) * Salary/30 as 'Total_Salary' 
    from Employees 
ELSE Select 
     EmpId, 
     Emp_Name, 
     Salary , 
     Start_date , 
     End_date , 
     DATEDIFF(End_Date, Start_Date) * Salary/30 as 'Total_Salary' 
    from Employees 
END 
From Employees; 

我已經嘗試了很多，但此查詢中的錯誤未得到解決。

我想區分如果結束日期爲null或不在表中的語句。

Answer 1

案例條款不起作用。您的查詢可以大大簡化如下。此外，列名稱和表名稱是使用back tick引用的，而不是單引號。

SELECT 
    `EmpId`, 
    `Emp_Name`, 
    `Salary`, 
    `Start_date`, 
    `End_dat`, 
    IF(`End_Date` is null, 
     DATEDIFF(DATE_ADD(`Start_Date`, INTERVAL 30 DAY), `Start_Date`) * `Salary`/30, 
     DATEDIFF(`End_Date`, `Start_Date`) * `Salary`/30) as `Total_Salary` 
FROM `Employees` 

Answer 2

試試這個：

SELECT EmpId, 
     Emp_Name, 
     Salary , 
     Start_date , 
     End_dat , 
    CASE 
     WHEN (Employees.End_Date is null) 
    THEN DATEDIFF(DATE_ADD(Start_Date, INTERVAL 30 DAY), Start_Date) * Salary/30 
    ELSE DATEDIFF(End_Date, Start_Date) * Salary/30 END AS Total_Salary 

From Employees;