主页 / dba / 问题 / 271037
Accepted
Deepan Kaviarasu
Asked: 2020-07-16 19:36:21 +0800 CST

按时间间隔分组并输出源和目的station_id和count

  • 772

我被一个查询困住了：

CREATE TABLE public.bulk_sample (
    serial_number character varying(255),
    validation_date timestamp,  -- timestamp of entry and exit
    station_id integer,
    direction integer           -- 1 = Entry | 2 = Exit
);

INSERT INTO public.bulk_sample VALUES
  ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 08:31:58', 120, 1)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 08:50:22', 113, 2)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 10:16:56', 113, 1)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 10:47:06', 120, 2)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 16:02:12', 120, 1)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 16:47:45', 102, 2)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 19:26:38', 102, 1)
, ('019b5526970fcfcf7813e9fe1acf8a41bcaf5a5a5c10870b3211d82f63fbf270', '2020-02-01 20:17:24', 120, 2)
, ('23cc9678e8cf834decb096ba36be0efee418402bce03aab52e69026adfec7663', '2020-02-01 07:58:20', 119, 1)
, ('23cc9678e8cf834decb096ba36be0efee418402bce03aab52e69026adfec7663', '2020-02-01 08:43:35', 104, 2)
, ('23cc9678e8cf834decb096ba36be0efee418402bce03aab52e69026adfec7663', '2020-02-01 16:38:10', 104, 1)
, ('23cc9678e8cf834decb096ba36be0efee418402bce03aab52e69026adfec7663', '2020-02-01 17:15:01', 119, 2)
, ('23cc9678e8cf834decb096ba36be0efee418402bce03aab52e69026adfec7663', '2020-02-01 17:42:29', 119, 1)
, ('23cc9678e8cf834decb096ba36be0efee418402bce03aab52e69026adfec7663', '2020-02-01 17:48:05', 120, 2)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 15:17:59', 120, 1)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 15:25:25', 118, 2)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 16:16:12', 118, 1)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 16:32:51', 120, 2)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 19:31:20', 120, 1)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 19:39:33', 118, 2)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 20:57:50', 118, 1)
, ('2a8f28bf0afc655210aa337aff016d33100282ac73cca660a397b924808499af', '2020-02-01 21:16:25', 120, 2)
;

我必须创建一个查询，其结果如下

source | dest | Count
120    | 113  |  1
113    | 120  |  1

我尝试了以下代码，但无法获得所需的结果：

SELECT serial_number
     , count(*)
     , min(validation_date) AS start_time
     , CASE WHEN count(*) > 1 THEN max(validation_date) END AS end_time
FROM  (
   SELECT serial_number, validation_date, count(step OR NULL) OVER (ORDER BY serial_number, 
validation_date) AS grp
   FROM  (
      SELECT *
           , lag(validation_date) OVER (PARTITION BY serial_number ORDER BY validation_date)
           < validation_date - interval '60 min' AS step
      FROM   table1 
       where BETWEEN '2020-02-01 00:00:00' AND '2020-02-01 23:59:59'
      ) sub1
   ) sub2
GROUP  BY serial_number, grp;

每次进出之间的时间间隔约为 55 分钟至 60 分钟。

我也尝试过内部联接，但无法按内部联接中的时间间隔进行分组

SELECT source.station_id AS source_station ,dest.station_id AS destination_station ,source.count FROM 
    (
        SELECT serial_number,station_id,count(bulk_transaction_id) FROM table1
        WHERE 
            direction = 1 AND 
            validation_date BETWEEN '2020-02-01 00:00:00' AND '2020-02-01 23:59:59' 
        GROUP BY serial_number,station_id
    )source

 INNER JOIN 
    (
        SELECT serial_number,station_id,count(bulk_transaction_id) FROM table1
        WHERE 
            direction = 2 AND 
            validation_date BETWEEN '2020-02-01 00:00:00' AND '2020-02-01 23:59:59'
        GROUP BY serial_number,station_id
    )dest
ON source.serial_number = dest.serial_number and source.station_id <> dest.station_id

挑战有时是进入日期为空，有时退出日期为空。

postgresql postgresql-10

2 个回答

  1. 为此，您将需要两件事：

    1. 连接条件的相关子查询
    2. (serial_number,validation_date) 上的唯一索引

    之后，您的查询变为：

    SELECT
  station_entry.station_id AS source
 ,station_exit.station_id AS dest
 ,COUNT(*) AS count
FROM
  public.bulk_sample station_entry
INNER JOIN
  public.bulk_sample station_exit
    ON station_exit.serial_number = station_entry.serial_number
        AND station_exit.validation_date =
              (
                SELECT
                  MIN(validation_date)
                FROM
                  public.bulk_sample
                WHERE
                  serial_number = station_entry.serial_number
                    AND validation_date > station_entry.validation_date
              )
WHERE
  station_entry.direction = 1
    AND station_exit.direction = 2  --Ensure next transaction is valid
    AND station_entry.validation_date >= '2020-02-01 00:00:00'
    AND station_entry.validation_date <= '2020-02-01 23:59:59'
    AND station_exit.validation_date <= '2020-02-01 23:59:59' --Ensure both events occurred within specified timeframe
GROUP BY
  station_entry.station_id
 ,station_exit.station_id

    应该返回：

    source  dest    count
102     120     1
104     119     1
113     120     1
118     120     2
119     104     1
119     120     1
120     102     1
120     113     1
120     118     2
    • 2
  2. Best Answer

    这应该是最简单和最快的，而每个事务serial_number从不重叠：

    WITH cte AS (
   SELECT serial_number, validation_date, station_id, direction
        , row_number() OVER (PARTITION BY serial_number ORDER BY validation_date) AS rn
   FROM   bulk_sample
   WHERE  validation_date >= '2020-02-01'  -- ①
   AND    validation_date <  '2020-02-02'  -- entry & exit must be within time frame
   )
SELECT s.station_id AS source, d.station_id AS dest, count(*)
FROM   cte s
JOIN   cte d USING (serial_number)
WHERE  s.direction = 1
AND    d.rn = s.rn + 1
GROUP  BY 1, 2
ORDER  BY 1, 2;  -- optional sort order

    db<>在这里摆弄

    ① 我重写了WHERE条件，以最佳方式获得 2020 年 2 月 1 日的所有内容。BETWEEN几乎总是时间范围的错误工具。看：

    此外，当时间分量丢失时，假定“2020-02-01”是一个完全有效的timestamp常数。00:00:00

    在检索给定时间范围内的结果时，一个普通的 btree索引是(validation_date)最佳的。对于完整的表，索引(serial_number, validation_date)会更有帮助。

    validation_date IS NULL?

    查询继续工作，而在给定时间范围内只有最后一个目的地有，因为值碰巧按默认升序排列在最后。但它与. 您必须更仔细地定义这些可以弹出的位置以及如何准确处理它们。serial_numbervalidation_date IS NULLNULLvalidation_date IS NULL

    (2x)uuid而不是varchar(255)for serial_number?

    您serial_number似乎是一个正好有 64 位数字的十六进制数。如果是这样，varchar(255)是一个糟糕的选择。看：

    此外，一个uuid（32 个十六进制数字）就足够了。如果需要所有 64 个十六进制数字，仍然考虑 2uuid列。更小、更快、更安全。考虑：

    SELECT *
     , replace(uuid1::text || uuid2::text, '-', '') AS reverse_engineered
     , replace(uuid1::text || uuid2::text, '-', '') = serial_number AS identical
     , pg_column_size(serial_number) AS varchar_size
     , pg_column_size(uuid1) + pg_column_size(uuid2) AS uuid_size
FROM  (
   SELECT serial_number
        , left(serial_number, 32)::uuid  AS uuid1
        , right(serial_number, 32)::uuid AS uuid2
   FROM   bulk_sample
   ) sub;

    db<>在这里摆弄

    看：

    • 1

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