SQL - 操作數數據類型datetime2對於減法運算符無效

Question

我想從列_timestamp（如下所示）的第二行的值中減去第一行的值。 _number是我數據中的排序列。

，並把結果在一個新列名爲差異。我試着用以下查詢

use dbtest 

select t2._number, t2._timestamp, 
coalesce(t2._timestamp - 
    (select t1._timestamp from dbo.tcp t1 where t1._number = t2._number + 1), t2._timestamp) as diff 
from dbo.tbl t2 

但我收到以下錯誤。

Msg 8117, Level 16, State 1, Line 4 
Operand data type datetime2 is invalid for subtract operator. 

任何提示將不勝感激。我有一個巨大的記錄，我想自動將它應用於整個列。我正在使用SQL Sever 2008.

Answer 1

正如評論中所述，您不能用-運算符減去時間戳。改用DATEDIFF函數。 要獲取當前行和下一行的時間戳的差異，請使用OUTER APPLY。

select t2._number,t2._timestamp, 
datediff(microsecond,t2._timestamp,t1._timestamp) as diff 
from dbo.tbl t2 
outer apply (select t1._timestamp 
      from dbo.tcp t1 
      where t1._number = t2._number + 1) t1 

編輯：update命名％的OP的評論DIFF

with cte as (   
select t2._number,t2._timestamp, t2.diff, 
datediff(microsecond,t2._timestamp,t1._timestamp) as diff_col 
from t t2 
outer apply (select t1._timestamp 
      from t t1 
      where t1._number = t2._number + 1) t1 
    ) 
update cte set diff=diff_col;