Question

我必须写一个T-SQL来获得超速行（最大/最小/平均），但条件是如果任何行＆lt; speedvalue然后将显示新的超速行

（Max / Min / avg）

例如，这是我的数据库表，如果此行超速

，则会有标记

rownum  Time                overspeed   overspeedrowid
1   2015-12-06 06:18:46.283 0           0
2   2015-12-06 06:19:46.283 1           0
3   2015-12-06 06:20:46.283 1           0
4   2015-12-06 06:21:46.283 0           0
5   2015-12-06 06:22:46.283 0           0
6   2015-12-06 06:23:46.283 1           0
7   2015-12-06 06:24:46.283 1           0
8   2015-12-06 06:25:46.283 1           0
9   2015-12-06 06:26:46.283 1           0
10  2015-12-06 06:27:46.283 0           0
11  2015-12-06 06:28:46.283 0           0
12  2015-12-06 06:29:46.283 0           0
13  2015-12-06 06:30:46.283 1           0
14  2015-12-06 06:31:46.283 1           0
15  2015-12-06 06:32:46.283 1           0
16  2015-12-06 06:33:46.283 0           0
17  2015-12-06 06:34:46.283 0           0
18  2015-12-06 06:35:46.283 1           0
19  2015-12-06 06:36:46.283 0           0
20  2015-12-06 06:37:46.283 0           0
21  2015-12-06 06:38:46.283 0           0
22  2015-12-06 06:39:46.283 1           0
23  2015-12-06 06:40:46.283 1           0

我的计划是使用以下

循环行，如果当前！= prev且prev = 0则为新的超速值
如果current = prev且prev = 1则当前的overspeedrowid = prev overspeedrowid
通过overspeedrowid从计算的表格最小/最大组中选择

所以计算的表格必须像这样

rownum  Time                overspeed   overspeedrowid
1   2015-12-06 06:18:46.283 0           0
2   2015-12-06 06:19:46.283 1           1
3   2015-12-06 06:20:46.283 1           1
4   2015-12-06 06:21:46.283 0           0
5   2015-12-06 06:22:46.283 0           0
6   2015-12-06 06:23:46.283 1           2
7   2015-12-06 06:24:46.283 1           2
8   2015-12-06 06:25:46.283 1           2
9   2015-12-06 06:26:46.283 1           2
10  2015-12-06 06:27:46.283 0           0
11  2015-12-06 06:28:46.283 0           0
12  2015-12-06 06:29:46.283 0           0
13  2015-12-06 06:30:46.283 1           3
14  2015-12-06 06:31:46.283 1           3
15  2015-12-06 06:32:46.283 1           3
16  2015-12-06 06:33:46.283 0           0
17  2015-12-06 06:34:46.283 0           0
18  2015-12-06 06:35:46.283 1           4
19  2015-12-06 06:36:46.283 0           0
20  2015-12-06 06:37:46.283 0           0
21  2015-12-06 06:38:46.283 0           0
22  2015-12-06 06:39:46.283 1           5
23  2015-12-06 06:40:46.283 1           5

我尝试了一个光标，但由于生产数据约为2,000,000行，因此需要很长时间。
我尝试使用连接第1行Update并将第1行与当前第1行进行比较，但未更正，因为它只更新了第二行

这是我所做的，但它只更新了第二行，

update #temp1 
set #temp1.overspeedrowid = @a, @a = @a + 1 
from #temp1 
left join #temp1 prev on prev.rownum = #temp1.rownum - 1 
where 
     (#temp1.overspeed != prev.overspeed and #temp1.overspeed = 1)

update #temp1 
set #temp1.overspeedrowid = prev. overspeedrowid 
from #temp1 
left join #temp1 prev on prev.rownum = #temp1.rownum - 1 
where 
     (#temp1.overspeed = prev.overspeed and #temp1.overspeed = 1)

Answer 1

在SQL Server 2012+中，您可以使用lag()后跟“条件”累积总和：

select t.*,
       (case when overspeed = 0 then 0
             else sum(OverSpeedFlag) over (order by time)
        end) as overspeedrowid
from (select t.*,
             (case when lag(overspeed) over (order by time) = 0 and overspeed = 1
                   then 1 else 0 
              end) as OverSpeedFlag
      from #temp1 t
     ) t;

SQL Server Group by Value！=没有Cursor循环的前一个值

1 个答案: