Question

我有一个数据库表，其中包含2列命名片和diff和类型。

这是表格的样子

id | piece | diff | type
1  | 20    | NULL | cake
2  | 15    | NULL | cake
3  | 10    | NULL | cake

我想要20 - 15 = 5然后15 -10 = 5，那么就这样堡垒就像在哪里。

结果将是这样的

id | piece | diff | type
1  | 20    | 0    | cake
2  | 15    | 5    | cake
3  | 10    | 5    | cake

这是我到目前为止的代码，但我不认为我在正确的轨道上

SELECT 
    tableblabla.id,
    (tableblabla.cast(pieces as decimal(7, 2)) - t.cast(pieces as decimal(7, 2))) as diff 
FROM 
    tableblabla
INNER JOIN
    tableblablaas t ON tableblabla.id = t.id + 1

感谢您的帮助

Answer 1

使用LAG/LEAD窗口功能。

考虑到您希望每Difference找到type，请从窗口函数中删除Partition by

select id, piece,
       Isnull(lag(piece)over(partition by type order by id) - piece,0) as Diff,
       type
From yourtable

如果您在Sql Server之前使用2012，请使用此功能。

;WITH cte
     AS (SELECT Row_number()OVER(partition by type ORDER BY id) RN,*
         FROM   Yourtable)
SELECT a.id,
       a.piece,
       Isnull(b.piece - a.piece, 0) AS diff,
       a.type
FROM   cte a
       LEFT JOIN cte b
              ON a.rn = b.rn + 1

从单列中减去数据

1 个答案: