考虑下表
表
ActivityId Flag Type
---------- ----- -----
1 N
2 N
3 Y EXT
4 Y
5 Y
6 N
7 Y INT
8 Y
9 N
10 N
11 N
12 Y EXT
13 N
14 N
15 N
16 Y EXT
17 Y
18 Y INT
19 Y
20 Y EXT
21 Y
22 N
23 N
第一条记录始终为Flag = N，然后下一条记录可以存在Flag = Y或Flag = N的任何序列。每次标记从N更改为Y时，Type字段都是EXT或INT。下一个Y记录（在下一个N之前）可能有Type = EXT或INT或NULL，这并不重要。
我想为此Cycle No序列计算N/Y。第一个周期从Flag = N开始（总是第一个记录有flag = N），当标志更改为Y和Type = EXT时，周期结束。然后，当标志更改为N时，下一个周期开始，当标志变为Y和type = EXT时结束。重复此过程，直到处理完所有记录。上表的结果是：
结果
ActivityId Flag Type Cycle No
---------- ----- ----- --------
1 N 1
2 N 1
3 Y EXT 1
4 Y
5 Y
6 N 2
7 Y INT 2
8 Y 2
9 N 2
10 N 2
11 N 2
12 Y EXT 2
13 N 3
14 N 3
15 N 3
16 Y EXT 3
17 Y
18 Y INT
19 Y
20 Y EXT
21 Y
22 N 4
23 N 4
我使用的是SQL Server 2008 R2（无LAG / LEAD）。
你能帮我找一下SQL查询来计算Cycle No吗？
答案 0 :(得分：3)
我有一个解决方案，它并不漂亮，但通过逐步细化，我得到了你的结果：
解决方案分为三个步骤
首先，我选择所有开始和结束周期事件：
with tab as
(select * from (values
(1,'N',''),(2,'N',''),(3,'Y','EXT'),(4,'Y','')
,(5,'Y',''),(6,'N',''),(7,'Y','INT'),(8,'Y','')
,(9,'N',''),(10,'N',''),(11,'N',''),(12,'Y','EXT')
,(13,'N',''),(14,'N',''),(15,'N',''),(16,'Y','EXT')
,(17,'Y',''),(18,'Y','INT'),(19,'Y',''),(20,'Y','EXT')
,(21,'Y',''),(22,'N',''),(23,'N','')) a(ActivityId,Flag,[Type]))
,CTE1 as
( select
ROW_NUMBER() over (order by t1.ActivityId) rn
,t1.ActivityId
,case when t1.Flag='N' then 'Start' else 'End' end Cycle
from tab t1
where t1.Flag='N' or (t1.Flag='Y' and t1.[Type]='Ext')
)
select * from cte1
返回
rn ActivityId Cycle
1 1 Start
2 2 Start
3 3 End
4 6 Start
5 9 Start
6 10 Start
7 11 Start
8 12 End
9 13 Start
10 14 Start
11 15 Start
12 16 End
13 20 End
14 22 Start
15 23 Start
现在的问题是，虽然我们确定循环何时结束，即当Flag为N且Type为Ext时，我们不确定循环何时开始。第1行和第2行都表示可能的启动事件。但幸运的是，我们可以看到只计算End事件后的启动事件。由于我们没有滞后或领先，我们必须加入CTE：
,CTE2 as
(
select ROW_NUMBER() over (order by a1.activityid) rn
,a1.ActivityId
,a1.Cycle
,a2.Cycle PrevCycle
from CTE1 a1 left join CTE1 a2 on a1.rn=a2.rn+1
where
a2.Cycle is null -- First Cycle
or
( a2.Cycle is not null
and
(
(a1.Cycle='End' and a2.Cycle='Start') -- End of cycle
or
(a1.Cycle='Start'
and a2.Cycle='End') -- next cycles
)
)
)
select * from cte2
返回
rn ActivityId Cycle PrevCycle
1 1 Start NULL
2 3 End Start
3 6 Start End
4 12 End Start
5 13 Start End
6 16 End Start
7 22 Start End
我选择第一个开始事件 - 因为我们总是从一个开始，然后保持开始事件后面的END事件。 最后，如果前一个事件是End事件，我们只保留其余的开始事件。
现在我们可以找到每个周期的开始和结束，并给它们编号：
,cte3 as
(
select ROW_NUMBER() over (order by b1.ActivityId) CycleNumber
,b1.ActivityId StartId,b2.ActivityId EndId
from cte2 b1 left join cte2 b2
on b1.rn=b2.rn-1
where b1.Cycle='Start'
)
select * from cte3
这给了我们所需要的东西：
CycleNumber StartId EndId
1 1 3
2 6 12
3 13 16
4 22 NULL
现在我们只需将这个加入我们的桌子：
select
a.ActivityId,a.Flag,a.[Type],CycleNumber
from tab a
left join cte3 b on a.ActivityId between b.StartId and isnull(b.EndId,a.ActivityId)
这给出了您正在寻找的结果。
这只是一个快速而肮脏的解决方案，也许只需要一点TLC就可以了，并减少步数。
完整的解决方案在这里：
with tab as
(select * from (values
(1,'N',''),(2,'N',''),(3,'Y','EXT'),(4,'Y','')
,(5,'Y',''),(6,'N',''),(7,'Y','INT'),(8,'Y','')
,(9,'N',''),(10,'N',''),(11,'N',''),(12,'Y','EXT')
,(13,'N',''),(14,'N',''),(15,'N',''),(16,'Y','EXT')
,(17,'Y',''),(18,'Y','INT'),(19,'Y',''),(20,'Y','EXT')
,(21,'Y',''),(22,'N',''),(23,'N','')) a(ActivityId,Flag,[Type]))
,CTE1 as
( select
ROW_NUMBER() over (order by t1.ActivityId) rn
,t1.ActivityId
,case when t1.Flag='N' then 'Start' else 'End' end Cycle
from tab t1
where t1.Flag='N' or (t1.Flag='Y' and t1.[Type]='Ext')
)
,CTE2 as
(
select ROW_NUMBER() over (order by a1.activityid) rn
,a1.ActivityId
,a1.Cycle
,a2.Cycle PrevCycle
from CTE1 a1 left join CTE1 a2 on a1.rn=a2.rn+1
where
a2.Cycle is null -- First Cycle
or
( a2.Cycle is not null
and
(
a1.Cycle='End' -- End of cycle
or
(a1.Cycle='Start'
and a2.Cycle='End') -- next cycles
)
)
)
,cte3 as
(
select ROW_NUMBER() over (order by b1.ActivityId) CycleNumber
,b1.ActivityId StartId,b2.ActivityId EndId
from cte2 b1 left join cte2 b2
on b1.rn=b2.rn-1
where b1.Cycle='Start'
)
select
a.ActivityId,a.Flag,a.[Type],CycleNumber
from tab a
left join cte3 b on a.ActivityId between b.StartId and isnull(b.EndId,a.ActivityId)
答案 1 :(得分：1)
如果您对递归感到满意，那么当您的ActivityId订购时，可以通过对前一行的一些比较逻辑来实现这一点：
declare @t table(ActivityId int,Flag nvarchar(1),TypeValue nvarchar(3));
insert into @t values(1 ,'N',null),(2 ,'N',null),(3 ,'Y','EXT'),(4 ,'Y',null),(5 ,'Y',null),(6 ,'N',null),(7 ,'Y','INT'),(8 ,'Y',null),(9 ,'N',null),(10,'N',null),(11,'N',null),(12,'Y','EXT'),(13,'N',null),(14,'N',null),(15,'N',null),(16,'Y','EXT'),(17,'Y',null),(18,'Y','INT'),(19,'Y',null),(20,'Y','EXT'),(21,'Y',null),(22,'N',null),(23,'N',null);
with rn as -- Derived table purely to guarantee incremental row number. If you can guarantee your ActivityId values are incremental start to finish, this isn't required.
( select row_number() over (order by ActivityId) as rn
,ActivityId
,Flag
,TypeValue
from @t
),d as
( select rn -- Recursive CTE that compares the current row to the one previous.
,ActivityId
,Flag
,TypeValue
,cast(1 as decimal(10,5)) as CycleNo
from rn
where rn = 1
union all
select rn.rn
,rn.ActivityId
,rn.Flag
,rn.TypeValue
,cast(
case when d.Flag = 'Y' and d.TypeValue = 'EXT' and d.CycleNo >= 1
then case when rn.Flag = 'N'
then d.CycleNo + 1
else (d.CycleNo + 1) * 0.0001 -- This part keeps track of the cycle number in fractional values, which can be removed by converting the final result to INT.
end
else case when rn.Flag = 'N' and d.CycleNo < 1
then d.CycleNo * 10000
else d.CycleNo
end
end
as decimal(10,5)) as CycleNo
from rn
inner join d
on d.rn = rn.rn - 1
)
select ActivityId
,Flag
,TypeValue
,cast(CycleNo as int) as CycleNo
from d
order by ActivityId;
输出：
+------------+------+-----------+---------+
| ActivityId | Flag | TypeValue | CycleNo |
+------------+------+-----------+---------+
| 1 | N | NULL | 1 |
| 2 | N | NULL | 1 |
| 3 | Y | EXT | 1 |
| 4 | Y | NULL | 0 |
| 5 | Y | NULL | 0 |
| 6 | N | NULL | 2 |
| 7 | Y | INT | 2 |
| 8 | Y | NULL | 2 |
| 9 | N | NULL | 2 |
| 10 | N | NULL | 2 |
| 11 | N | NULL | 2 |
| 12 | Y | EXT | 2 |
| 13 | N | NULL | 3 |
| 14 | N | NULL | 3 |
| 15 | N | NULL | 3 |
| 16 | Y | EXT | 3 |
| 17 | Y | NULL | 0 |
| 18 | Y | INT | 0 |
| 19 | Y | NULL | 0 |
| 20 | Y | EXT | 0 |
| 21 | Y | NULL | 0 |
| 22 | N | NULL | 4 |
| 23 | N | NULL | 4 |
+------------+------+-----------+---------+