Question

我希望在选择的syntac sql中执行算术运算，例如10减5 = 5，但我的选择不起作用。

select DATEDIFF(MINUTE,on_duty, clock_in ) as late, DATEDIFF(MINUTE ,off_duty, clock_out ) as Early, late - Early as jajalan from kkpsurabaya

look image pls

Answer 1

由于解析查询的方式，您不能在SELECT和ORDER BY之外的同一个select中使用该函数的结果，因为you cannot refer to an alias。你可以多次调用同一个函数：

select DATEDIFF(MINUTE,on_duty, clock_in ) as late, 
       DATEDIFF(MINUTE ,off_duty, clock_out ) as Early, 
       DATEDIFF(MINUTE,on_duty, clock_in )- DATEDIFF(MINUTE ,off_duty, clock_out ) as jajalan 
from kkpsurabaya

或共同表格：

WITH CTE AS
(
    SELECT DATEDIFF(MINUTE,on_duty, clock_in ) as Late,
    DATEDIFF(MINUTE ,off_duty, clock_out ) as Early,
    t.*
    FROM kkpsurabaya t  
)
SELECT Late, Early, Late - Early as jajalan
FROM CTE

SQL。语法选择执行算术运算

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