SQL迭代没有游标的行

Question

我有一些读取传感器状态的数据。传感器每 15 分钟报告一次状态。这有点像......

Sensor ID, Status, TimeStamp, **WhatIWantSessionID**
1, Off, 0345, **0**
1, Charge, 0400, **1**
1, Charge, 0415, **1**
1, Off, 0430, **0**
1, Charge, 0445, **2**
1, Off, 0500, **0** 

"WhatIWantSessionID" ...我想在每次 Charge 会话开始时设置一个递增的 sessionID。保持该 sessionID 直到状态切换状态。以下链接非常棒，“几乎”可以满足我的需要，但并不完全（因为我没有在会话中开始/停止的标志）。非常感谢帮助。 Iterate over rows using SQL

Answer 1

必须有更好的方法来做到这一点，但下面的例子有效（丑陋，我相信有人会发布一些聪明而聪明的东西，但我今天还没有足够的咖啡来做聪明，并且有效）。

create or replace temporary table stacko_64351844 (
    id number,
    status varchar(20),
    ts     varchar(20),
    desired number);

INSERT INTO stacko_64351844 
VALUES 
(1, 'Off', '0345', 0),
(1, 'Charge', '0400', 1),
(1, 'Charge', '0415', 1),
(1, 'Off', '0430', 0),
(1, 'Charge', '0445', 2),
(1, 'Off', '0500', 0),
(1, 'Charge', '0515', 3),
(1, 'Charge', '0530', 3),
(1, 'Charge', '0545', 3),
(1, 'Charge', '0600', 3),
(1, 'Off', '0615', 0);

SELECT id,
       status, ts,
       desired,
       NVL(calc_desired, max(calc_desired) over (partition by id  order by id, ts rows between unbounded preceding and current row)) as calc_desired
FROM (
SELECT id, 
       status, 
       ts, 
       desired,
       tmp_desired,
       CASE
         WHEN status = 'Off' THEN 0
         WHEN (status != 'Charge' AND status = lag(status, 1, null)
              over (partition by id order by id, ts, status DESC) )
               THEN null
         ELSE
           sum(tmp_desired) over (partition by id, tmp_desired order by id, ts rows between unbounded preceding and current row)
       end as calc_desired
FROM (
  SELECT id, 
         status, 
         ts, 
         desired, 
         CASE
         WHEN status = 'Off' THEN 0
         WHEN status = lag(status, 1, null) 
              over (partition by id order by id, ts, status DESC) 
               THEN null
         ELSE
           1
       end  as tmp_desired
  FROM   stacko_64351844)
ORDER BY id, ts, status DESC);

RESULTS
ID  STATUS  TS  DESIRED CALC_DESIRED
1   Off     0345    0   0
1   Charge  0400    1   1
1   Charge  0415    1   1
1   Off     0430    0   0
1   Charge  0445    2   2
1   Off     0500    0   0
1   Charge  0515    3   3
1   Charge  0530    3   3
1   Charge  0545    3   3
1   Charge  0600    3   3
1   Off     0615    0   0

我希望这会有所帮助...丰富

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Answer 2

MSSQL，但肯定/希望它能在 ansi 上运行。 感谢 Rich Murnane 提供数据提示

create TABLE  #stacko_64351844 (
    id int,
    status varchar(20),
    ts     varchar(20),
    desired int);

INSERT INTO #stacko_64351844 
VALUES 
(1, 'Off', '0345', 0),
(1, 'Charge', '0400', 1),
(1, 'Charge', '0415', 1),
(1, 'Off', '0430', 0),
(1, 'Charge', '0445', 2),
(1, 'Off', '0500', 0),
(1, 'Charge', '0515', 3),
(1, 'Charge', '0530', 3),
(1, 'Charge', '0545', 3),
(1, 'Charge', '0600', 3),
(1, 'Off', '0615', 0);

SELECT  CASE status WHEN 'off' THEN 0
 else SUM(CASE WHEN lg='off' THEN 1 ELSE 0 END) OVER(PARTITION BY id ORDER BY ts) END DesiredCalc       
,t.id,t.status,t.ts,t.desired FROM  (
    SELECT LAG(status)OVER(PARTITION BY id ORDER BY ts)lg,* FROM #stacko_64351844 
)t
ORDER BY ts

结果：

DesiredCalc id  status  ts  desired
0   1   Off 0345    0
1   1   Charge  0400    1
1   1   Charge  0415    1
0   1   Off 0430    0
2   1   Charge  0445    2
0   1   Off 0500    0
3   1   Charge  0515    3
3   1   Charge  0530    3
3   1   Charge  0545    3
3   1   Charge  0600    3
0   1   Off 0615    0