Question

RecordNo    Speed  
--------    -----
1           0
2           0
3           0
4           0
5           23
6           66
7           48
8           0
9           31
10          0
11          34
12          23

以上数据显示了一段时间内车辆的速度，鉴于以上数据我需要达到以下结果：

RecordNo    Speed   LastAcceleration
--------    -----   ----------------
1           0       0
2           0       0
3           0       0
4           0       0
5           23      23
6           66      66
7           48      66
8           0       66
9           31      31
10          0       31
11          34      34
12          23      34

下面的代码几乎就在那里，但在Recordno 8：

select
curr.recordno,curr.speed 
,CASE WHEN curr.speed >= ISNULL(prev.speed,0) THEN curr.speed
    ELSE (
            SELECT MAX(speed) FROM speedtest 
            WHERE recordno between (CASE WHEN curr.speed >= prev.speed then curr.recordindex else prev.recordno end ) and curr.recordno 
          ) 
END as LastAcceleration
From speedtest prev RIGHT JOIN speedtest curr
on prev.vrm = curr.vrm
and prev.recordno+1 = curr.recordno
order by curr.recordno

我想我一直盯着这个太久了。我尝试过使用相关子查询进行自联接，但是我觉得我错过了一些明显的东西？这是针对2008项目的，因此不必使用之前的任何版本。任何帮助将不胜感激。

Answer 1

你走了！你基本上错过了你需要检查最新加速度的部分，只要它没有加速（我的查询中不存在的部分更多）

create table #t (recordno int, speed int)
insert into #t
select 1,           0
union select 2,           0
union select 3,           0
union select 4,           0
union select 5,           23
union select 6,           66
union select 7,           48
union select 8,           0
union select 9,           31
union select 10,          0
union select 11,          34
union select 12,          23

;with acc as (
select
    t1.*,
    case when t1.speed >= isnull(t2.speed, 0) then t1.speed else -1 end as 'accel'
from
    #t t1
    left join #t t2
        on  t1.recordno = t2.recordno + 1
)

select 
    a.recordno, a.speed, 
    case 
        when a.accel >= 0 then a.accel 
        else (
            select accel 
            from acc a1 
            where a1.recordno < a.recordno and a1.accel >= 0 
                and not exists (
                    select 1 
                    from acc a2 
                    where a2.recordno < a.recordno and a2.accel >= 0 and a2.recordno > a1.recordno)
            )
    end
from
    acc a

drop table #t

Answer 2

你可以这样做：

declare @t table(recordno int, speed int) 
insert into @t select 1,           0 
union select 2,           0 
union select 3,           0 
union select 4,           0 
union select 5,           23 
union select 6,           66 
union select 7,           48 
union select 8,           0 
union select 9,           31 
union select 10,          0 
union select 11,          34 
union select 12,          23 

;with a as
(
select recordno, speed, 0 LastAcceleration from @t
where recordno = 1
union all
select b.recordno, b.speed, 
    case when b.speed > LastAcceleration then b.speed else 
    case when a.speed = 0 then b.speed else LastAcceleration end end
from a join @t b on b.recordno - 1 = a.recordno
)
select recordno, speed, LastAcceleration from a
option (maxrecursion 0)

仅在增加的范围内找到最高电流数

2 个答案: