SQL - 按条目 X 彼此相隔的时间对表进行分组答案

【问题标题】：SQL - Group Table by entries X amount of time from each otherSQL - 按条目 X 彼此相隔的时间对表进行分组
【发布时间】：2016-05-16 23:49:25
【问题描述】：

我需要将其中一个和另一个之间的时间戳差异为 X 秒或小于 X 秒数的条目组合在一起，然后为每个设备对每个条目的值进行平均。在下面的示例中，我有一个包含此数据的表，我需要按设备分组，条目之间的间隔在 60 秒之间。

          Device            Timestamp  Value
0  30:8c:fb:a4:b9:8b  10/26/2015 22:50:15     34
1  30:8c:fb:a4:b9:8b  10/26/2015 22:50:46     34
2  c0:ee:fb:35:ec:cd  10/26/2015 22:50:50     33
3  c0:ee:fb:35:ec:cd  10/26/2015 22:50:51     32
4  30:8c:fb:a4:b9:8b  10/26/2015 22:51:15     34
5  30:8c:fb:a4:b9:8b  10/26/2015 22:51:47     32
6  c0:ee:fb:35:ec:cd  10/26/2015 22:52:38     38
7  30:8c:fb:a4:b9:8b  10/26/2015 22:54:46     34

这应该是结果表

          Device           First_seen            Last_seen Average_value
0  30:8c:fb:a4:b9:8b  10/26/2015 22:50:15  10/26/2015 22:51:47          33,5
1  c0:ee:fb:35:ec:cd  10/26/2015 22:50:50  10/26/2015 22:50:51          32,5
2  c0:ee:fb:35:ec:cd  10/26/2015 22:52:38  10/26/2015 22:52:38            38
3  30:8c:fb:a4:b9:8b  10/26/2015 22:54:46  10/26/2015 22:54:46            34

非常感谢您的帮助。

【问题讨论】：

标签： mysql sql google-bigquery

【解决方案1】：

这有一个老把戏！
主要基于Window functions的力量
非常适合 BigQuery！

所以，首先你“标记”所有在上一个条目之后超过 60 秒的条目！
超过取值 1 其余取值为 0 的！

其次，您通过对所有先前标记求和来定义组（当然，上述步骤是在按设备分区时完成的）

最后，您只需按上述定义的组进行简单分组

在一个查询中实现三个简单的步骤，只需几个简单的子选择！
希望这会有所帮助

SELECT device, MIN(ts) AS first_seen, MAX(ts) AS last_seen, AVG(value) AS average_value
FROM (
  SELECT device, ts, value, SUM(grp_start) OVER (PARTITION BY device ORDER BY ts) AS grp
  FROM (
   SELECT device, ts, value, 
   IF(TIMESTAMP_TO_SEC(TIMESTAMP(ts))-TIMESTAMP_TO_SEC(TIMESTAMP(ts0))>60,1,0) AS grp_start
   FROM (
      SELECT device, ts, value, LAG(ts, 1) OVER(PARTITION BY device ORDER BY ts) AS ts0
      FROM yourTable
    )
  )
)
GROUP BY device, grp

【讨论】：

【解决方案2】：

这是一种方法...

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(device CHAR(1) NOT NULL
,timestamp DATETIME NOT NULL
,value INT NOT NULL
,PRIMARY KEY(device,timestamp)
);

INSERT INTO my_table VALUES
('a','2015/10/26 22:50:15',34),
('a','2015/10/26 22:50:46',34),
('b','2015/10/26 22:50:50',33),
('b','2015/10/26 22:50:51',32),
('a','2015/10/26 22:51:15',34),
('a','2015/10/26 22:51:47',32),
('b','2015/10/26 22:52:38',38),
('a','2015/10/26 22:54:46',34);



SELECT m.*
     , AVG(n.value) avg
  FROM 
     ( SELECT a.device
            , a.timestamp start
            , MIN(c.timestamp) end 
         FROM 
            ( SELECT x.*
                   , CASE WHEN x.device = @prev THEN @i:=@i+1 ELSE @i:=1 END i
                   , @prev:=device 
                FROM my_table x
                   , (SELECT @i:=1,@prev:=null) vars 
               ORDER 
                  BY device
                   , timestamp
            ) a
         LEFT 
         JOIN 
            ( SELECT x.*
                   , CASE WHEN x.device = @prev THEN @i:=@i+1 ELSE @i:=1 END i
                   , @prev:=device 
                FROM my_table x
                   , (SELECT @i:=1,@prev:=null) vars 
               ORDER 
                  BY device
                   , timestamp
            ) b
           ON b.device = a.device
          AND b.timestamp > a.timestamp - INTERVAL 60 SECOND
          AND b.i = a.i - 1
         LEFT 
         JOIN 
            ( SELECT x.*
                   , CASE WHEN x.device = @prev THEN @i:=@i+1 ELSE @i:=1 END i
                   , @prev:=device 
                FROM my_table x
                   , (SELECT @i:=1,@prev:=null) vars 
               ORDER 
                  BY device
                   , timestamp
            ) c
           ON c.device = a.device
          AND c.i >= a.i
         LEFT 
         JOIN 
            ( SELECT x.*
                   , CASE WHEN x.device = @prev THEN @i:=@i+1 ELSE @i:=1 END i
                   , @prev:=device 
                FROM my_table x
                   , (SELECT @i:=1,@prev:=null) vars 
               ORDER 
                  BY device
                   , timestamp
            ) d 
           ON d.device = c.device
          AND d.i = c.i + 1
          AND d.timestamp < c.timestamp + INTERVAL 60 SECOND
        WHERE b.i IS NULL 
          AND c.i IS NOT NULL
          AND d.i IS NULL
        GROUP 
           BY a.device
            , a.i
            ) m
         JOIN my_table n
           ON n.device = m.device
          AND n.timestamp BETWEEN start AND end
        GROUP
           BY m.device 
            , m.start;

+--------+---------------------+---------------------+---------+
| device | start               | end                 | avg     |
+--------+---------------------+---------------------+---------+
| a      | 2015-10-26 22:50:15 | 2015-10-26 22:51:47 | 33.5000 |
| a      | 2015-10-26 22:54:46 | 2015-10-26 22:54:46 | 34.0000 |
| b      | 2015-10-26 22:50:50 | 2015-10-26 22:50:51 | 32.5000 |
| b      | 2015-10-26 22:52:38 | 2015-10-26 22:52:38 | 38.0000 |
+--------+---------------------+---------------------+---------+

【讨论】：