使用 T-SQL 中行的先前值计算值

Question

我得到了下表，想在不使用游标或 while 循环的情况下使用 sql 中前一行的同一列 (Column2) 的值来计算每一行的 Column2 的值。

Id   Date             Column1    Column2
1    01/01/2011       5          5 => Same as Column1
2    02/01/2011       2          18 => (1 + (value of Column2 from the previous row)) * (1 + (Value of Column1 from the current row)) i.e. (1+5)*(1+2)
3    03/01/2011       3          76 => (1+18)*(1+3) = 19*4
and so on

有什么想法吗？

---

Answer 1

假设recursive CTE 至少为 SQL Server 2005：

;with cteCalculation as (
    select t.Id, t.Date, t.Column1, t.Column1 as Column2
        from YourTable t
        where t.Id = 1
    union all
    select t.Id, t.Date, t.Column1, (1+t.Column1)*(1+c.Column2) as Column2
        from YourTable t
            inner join cteCalculation c
                on t.Id-1 = c.id
)
select c.Id, c.Date, c.Column1, c.Column2
    from cteCalculation c

Answer 2

我解决了刚才提到的问题。

这是我的代码：

;with cteCalculation as (
    select t.Id, t.Column1, t.Column1 as Column2
        from table_1 t
        where t.Id = 1
    union all
    select t.Id, t.Column1, (1+t.Column1)*(1+c.Column2) as Column2
        from table_1 t
            inner join cteCalculation c
                on t.Id-1 = c.id
),
cte2 as(
select t.Id, t.Column1 as Column3
        from table_1 t
        where t.Id = 1
    union all
    select t.Id, (select column2+1 from cteCalculation c where c.id = t.id)  as Column3
        from table_1 t
            inner join cte2 c2
                on t.Id-1 = c2.id
)

select c.Id, c.Column1, c.Column2, c2.column3
    from cteCalculation c
inner join cte2 c2 on c.id = c2.id

结果如我所料：

1           5   5   5
2           2   18  19
3           3   76  77

Answer 3

这是一个使用 ROW_NUMBER() 的示例，如果 Id 不一定按顺序排列：

;with DataRaw as (
    select 1 as Id, '01/01/11' as Date, 5 as Column1 union
    select 2 as Id, '02/01/11' as Date, 2 as Column1 union
    select 4 as Id, '03/01/11' as Date, 3 as Column1
),
Data as (
    select RowId = ROW_NUMBER() over (order by Id), Id, Date, Column1 from DataRaw
),
Data2 as (
    select
        RowId, id, Date, Column1, Column1 as Column2
    from
        Data d
    where
        RowId = 1

    union all

    select
        d1.RowId, d1.id, d1.Date, d1.Column1, (1+d1.column1)*(1+d2.column2) as column2
    from
        Data d1
    cross join
        Data2 d2
    where
        d2.RowId + 1 = d1.RowId
)
select
    Id, Date, Column1, Column2
from
    Data2

Answer 4

编辑：应该更好地阅读这个问题......

另一场比赛是这样的：

;with DataRaw as (
    select 1 as Id, '01/01/11' as Date, 5 as Column1 union
    select 2 as Id, '02/01/11' as Date, 2 as Column1 union
    select 4 as Id, '03/01/11' as Date, 3 as Column1
),
Data as (
    select Ord = ROW_NUMBER() over (order by Id), Id, Date, Column1 from DataRaw
),
select -- formula goes here, using current and prev as datasources.
from  data current
      left join data prev on current.Ord = prev.Ord + 1  -- pick the previous row by adding 1 to the ordinal

我认为到达前一行的普通连接会比 CTE 更快。不过，您必须自己检查。

对我来说看起来更容易。

祝你好运，GJ