Create Table A
(a Int)
--插入數據
Insert A Select 15
Union All Select 17
Union All Select 19
Union All Select 22
--測試
Select
T.a,
(T.a-(Select Top 1 a from A Where a<T.a Order By a Desc)) As 列差
from A T
--刪除測試環境
Drop Table A
--結果
/*
a 列差
15 NULL
17 2
19 2
22 3