SQL

Question

我在 table 中有数据显示点火 true 或 false

|--------------------------------------|
|             date          | ignition |
|---------------------------|----------|
|2019-06-03 10:15:00.000000 | false    |
|---------------------------|----------|
|2019-06-03 10:30:00.000000 | false    |
|---------------------------|----------|
|2019-06-03 11:30:00.000000 | true     |
|---------------------------|----------|
|2019-06-03 11:45:00.000000 | false    |
|---------------------------|----------|
|2019-06-03 11:55:00.000000 | false    |
|---------------------------|----------|

我写了 SQL 显示日期期间点火状态的查询

SELECT min(date) as date_from, max(date) as date_to, ignition
FROM (SELECT date,
             ignition,
             row_number() over (order by date) as seqnum,
             row_number() over (partition by ignition order by date) as seqnum_s
      FROM table_data
      WHERE date >= '2019-06-01T21:00:00.000Z' AND date <= '2019-06-09T20:59:59.999Z'
    ) as raw_data
GROUP BY (seqnum - seqnum_s), ignition
ORDER BY min(date);

查询结果：

|---------------------------|----------------------------|----------|
|             date_from     | date_to                    | ignition |
|---------------------------|----------------------------|----------|
|2019-06-03 10:15:00.000000 | 2019-06-03 10:30:00.000000 | false    |
|---------------------------|----------------------------|----------|
|2019-06-03 11:30:00.000000 | 2019-06-03 11:30:00.000000 | true     |
|---------------------------|----------------------------|----------|
|2019-06-03 11:45:00.000000 | 2019-06-03 11:55:00.000000 | false    |
|---------------------------|----------------------------|----------|

但结果中缺少从 10:30 到 11:30 的日期和从 11:30 到 11:45 的日期。我应该得到这个：

|---------------------------|----------------------------|----------|
|             date_from     | date_to                    | ignition |
|---------------------------|----------------------------|----------|
|2019-06-03 10:15:00.000000 | 2019-06-03 11:30:00.000000 | false    |
|---------------------------|----------------------------|----------|
|2019-06-03 11:30:00.000000 | 2019-06-03 11:45:00.000000 | true     |
|---------------------------|----------------------------|----------|
|2019-06-03 11:45:00.000000 | 2019-06-03 11:55:00.000000 | false    |
|---------------------------|----------------------------|----------|

问题是在聚合成一个块时（例如 false 后面的 5 行）他只查看 false 的最后一行来确定块的结束时间，而不是接下来的第一行（第一个是真）

Answer 1

OK，就用window函数lead得到下一行的值date_from，然后把这个值设置到当前行的date_to，SQL如下：

select 
    date_from,
    case when lead(date_from,1) over(order by date_from) is null then date_to else lead(date_from,1) over(order by date_from) end as date_to,
    ignition
from (
SELECT min(date) as date_from, max(date) as date_to, ignition
FROM (SELECT date,
             ignition,
             row_number() over (order by date) as seqnum,
             row_number() over (partition by ignition order by date) as seqnum_s
      FROM table_data
      WHERE date >= '2019-06-01T21:00:00.000Z' AND date <= '2019-06-09T20:59:59.999Z'
    ) as raw_data
GROUP BY (seqnum - seqnum_s), ignition
ORDER BY min(date)
) tmp;
      date_from      |       date_to       | ignition 
---------------------+---------------------+----------
 2019-06-03 10:15:00 | 2019-06-03 11:30:00 | f
 2019-06-03 11:30:00 | 2019-06-03 11:45:00 | t
 2019-06-03 11:45:00 | 2019-06-03 11:55:00 | f
(3 rows)

Answer 2

更简单的表达方式是：

SELECT min(date) as date_from,
       lead(min(date)) over (order by min(date)) as date_to,
       ignition
FROM (SELECT d.*,
             row_number() over (order by date) as seqnum,
             row_number() over (partition by ignition order by date) as seqnum_s
      FROM table_data d
      WHERE date >= '2019-06-01T21:00:00.000Z' AND date < '2019-06-09T21:00:00Z'
     ) as raw_data
GROUP BY (seqnum - seqnum_s), ignition
ORDER BY min(date)

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