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SQL中分组时间序列的最小值和最大值

window-functions postgresql sql

the_darkside · 技术社区 · 6 年前

test 我想从中提取序列 no_signal mobile_id

在真正的表中,记录没有排序,我认为这意味着 PARTITION OVER (time, mobile_id )除了窗口函数外,还必须包含语句。任何关于如何为单个连续序列创建一个组,然后取每个组的最小值和最大值的建议都将不胜感激。

-- CREATE TABLE test (mobile_id int, state varchar, time timestamp, region varchar)

INSERT INTO test (mobile_id, state, time, region ) VALUES
(1, 'active', TIMESTAMP '2018-08-09 15:00:00', 'EU'),  
(1, 'active', TIMESTAMP '2018-08-09 16:00:00', 'EU'),
(1, 'no_signal', TIMESTAMP '2018-08-09 17:00:00', 'EU'),
(1, 'no_signal', TIMESTAMP '2018-08-09 18:00:00', 'EU'),
(1, 'no_signal', TIMESTAMP '2018-08-09 19:00:00', 'EU'),
(1, 'active', TIMESTAMP '2018-08-09 20:00:00', 'EU'),
(1, 'inactive', TIMESTAMP '2018-08-09 21:00:00', 'EU'),
(1, 'active', TIMESTAMP '2018-08-09 22:00:00', 'EU'),
(1, 'active', TIMESTAMP '2018-08-09 23:00:00', 'EU'),
(2, 'active', TIMESTAMP '2018-08-10 00:00:00', 'EU'),
(2, 'no_signal', TIMESTAMP '2018-08-10 01:00:00', 'EU'),
(2, 'active', TIMESTAMP '2018-08-10 02:00:00', 'EU'),
(2, 'no_signal', TIMESTAMP '2018-08-10 03:00:00', 'EU'),
(2, 'no_signal', TIMESTAMP '2018-08-10 04:00:00', 'EU'),
(2, 'no_signal', TIMESTAMP '2018-08-10 05:00:00', 'EU'),
(2, 'no_signal', TIMESTAMP '2018-08-10 06:00:00', 'EU'),
(3, 'active', TIMESTAMP '2018-08-10 07:00:00', 'SA'),
(3, 'active', TIMESTAMP '2018-08-10 08:00:00', 'SA'),
(3, 'no_signal', TIMESTAMP '2018-08-10 09:00:00', 'SA'),
(3, 'no_signal', TIMESTAMP '2018-08-10 10:00:00', 'SA'),
(3, 'inactive', TIMESTAMP '2018-08-10 11:00:00', 'SA'),
(3, 'inactive', TIMESTAMP '2018-08-10 12:00:00', 'SA'),
(3, 'no_signal', TIMESTAMP '2018-08-10 13:00:00', 'SA')

我的目标输出如下:

 mobile_id          start_time            end_time diff_time region
         1 2018-08-09 17:00:00 2018-08-09 19:00:00       120     EU
         2 2018-08-10 01:00:00 2018-08-10 01:00:00         0     EU
         2 2018-08-10 03:00:00 2018-08-10 06:00:00       180     EU
         3 2018-08-10 09:00:00 2018-08-10 10:00:00        60     SA
         3 2018-08-10 13:00:00 2018-08-10 13:00:00         0     SA

由于未正确创建组,以下代码不会产生所需的结果:

select mobile_id, region,
       least(extract(epoch from max(time) - min(time)), 0) as diff
from (select t.*,
             count(*) filter (where state = 'no_signal) over (partition by mobile_id, region order by time) as grp
      from t
     ) t
group by mobile_id, region, grp;

2 回复 | 直到 6 年前

Tim Biegeleisen 6 年前

这是缺口和孤岛问题的一个变种。在本例中,您尝试检测具有 no_signal 每个手机号码。

ROW_NUMBER 在你的桌子上有两种方式。第一个生成所有记录的序列,按时间排序,而第二个生成每个记录的序列 mobile_id 无\u信号 . 这个差异在这些行中,数字值可用于形成每个岛。然后,我们只需聚合并获取min/max timestamp值即可得到所需的结果。

WITH cte1 AS (
    SELECT *, ROW_NUMBER() OVER (ORDER BY time) rn1
    FROM test
),
cte2 AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY mobile_id ORDER BY time) rn2
    FROM test
    WHERE state = 'no_signal'
),
cte3 AS (
    SELECT t1.*, t2.rn2
    FROM cte1 t1
    LEFT JOIN cte2 t2
        ON t1.mobile_id = t2.mobile_id AND t1.time = t2.time
    WHERE t1.state = 'no_signal'
)

SELECT
    mobile_id,
    MIN(time) AS start_time,
    MAX(time) AS end_time,
    EXTRACT(epoch FROM MAX(time::timestamp) - MIN(time::timestamp)) / 60 diff_time,
    region
FROM cte3
GROUP BY
    mobile_id,
    region,
    (rn1 - rn2)
ORDER BY
    mobile_id,
    start_time;

Demo

Tim Biegeleisen 6 年前

demo: db<>fiddle

SELECT DISTINCT
    mobile_id,
    first_value(time) over (partition by ranked, time) as start_time,        -- B
    first_value(time) over (partition by ranked, time desc) as end_time, 
    region
FROM
(
    SELECT *, SUM(is_diff) OVER (ORDER BY time) as ranked                          -- A
    FROM
    (
        SELECT *,
            CASE WHEN state = lag(state) over (order by time) THEN 0 ELSE 1 END as is_diff
        FROM test 
    ) s
) s
WHERE
    state = 'no_signal';

答:问题是您试图对一列进行排序,然后又想对另一列进行分区。这个问题可以通过这个子查询来解决。讨论了这个问题 here

B:你的窗户造好之后 start_time end_time 通过使用 first_value(time) 和 first_value(time) ... ORDER BY time DESC 功能。 DESC 因为它用最新时间对窗口排序,然后你可以得到它的第一个值( last_value() does not work as expected every time ).

为了更清楚地了解真正的问题,我省略了 diff 上面的计算:添加 差异

SELECT 
    *,  
    EXTRACT(epoch from (end_time - start_time)) / 60 as diff
FROM (
    -- <QUERY ABOVE>
) s