为Postgres中不存在的行显示逗号分隔的值

基本问题是生成时间间隔和数据集id,而不是从数据中读取它们。这会影响 dataset_full CTE。你似乎只想要数据中某个地方的值。

因此:

with dataset as (
      select *
      from (values ('2010-04-14T00:00'::TIMESTAMP, 12.6941, 12.6941, 12.6941, 12.6941, 1),
                   ('2010-04-14T00:00'::TIMESTAMP, 12.3851, 12.3851, 12.3851, 12.3851, 2),
                   ('2010-04-14T00:20'::TIMESTAMP, 12.389, 12.389, 12.389, 12.389, 1),
                   ('2010-04-14T00:20'::TIMESTAMP, 12.1836, 12.1836, 12.1836, 12.1836, 2),
                   ('2010-04-14T00:20'::TIMESTAMP, 11.3887, 11.3887, 11.3887, 11.3887, 13)
           ) AS data(t, mean, max, min, std, data_id)
      ),
     dataset_full as (
       select t.t, d.data_id,
              ds.mean, ds.max, ds.min, ds.std
       from (select distinct t from dataset) t cross join
            (select distinct data_id from dataset) d left join
            dataset ds
            on ds.t = t.t and ds.data_id = d.data_id
     )
select t,string_agg(concat(mean, ',', max, ',', min, ',', std), ',' order by data_id)
from dataset_full
group by t
order by t;

Here 是SQL小提琴。

还要注意 order by 在 string_agg() . 假设您希望这些值按 dataset_id .

你可以替换 LEFT JOIN 具有 JOIN :

WITH dataset AS (
    SELECT *
    FROM(VALUES
     ('2010-04-14T00:00'::TIMESTAMP, 12.6941, 12.6941, 12.6941, 12.6941, 1),
     ('2010-04-14T00:00'::TIMESTAMP, 12.3851, 12.3851, 12.3851, 12.3851, 2),
     ('2010-04-14T00:20'::TIMESTAMP, 12.389, 12.389, 12.389, 12.389, 1),
     ('2010-04-14T00:20'::TIMESTAMP, 12.1836, 12.1836, 12.1836, 12.1836, 2),
     ('2010-04-14T00:20'::TIMESTAMP, 11.3887, 11.3887, 11.3887, 11.3887, 13)
     ) AS data(t, mean, max, min, std, data_id)
),
dataset_full AS (
    SELECT coalesce(t, time) AS t,
        mean,
        max,
        min,
        std,
        data_id
    FROM generate_series(
                (SELECT min(t) FROM dataset),
                (SELECT max(t) FROM dataset),
                '10 minutes')
            AS times(time)
        CROSS JOIN generate_series(
                       (SELECT min(data_id) FROM dataset),
                       (SELECT max(data_id) FROM dataset))
            AS data_id(id)
        JOIN dataset    -- here
          ON times.time = dataset.t 
         AND data_id.id = dataset.data_id
)
SELECT t,string_agg(concat(mean, ',', max, ',', min, ',', std), ',')
FROM dataset_full
GROUP BY t
ORDER BY t;

DBFiddle Demo

编辑:

第一行的,,,,被删除,我不想

...
 cte2 AS (
  SELECT    t,   string_agg(concat(mean, ',', max, ',', min, ',', std), ',') AS s
       , COUNT(*) AS c
  FROM dataset_full
  GROUP BY t
)
SELECT t, s|| REPEAT(',,,,', (MAX(c) OVER() - c)::int)
FROM cte2
ORDER BY t; 

DBFiddle Demo2

输出:

┌─────────────────────┬─────────────────────────────────────────────────────────────────────────────────────────────┐
│ t                   │ result                                                                                      │
├─────────────────────┼─────────────────────────────────────────────────────────────────────────────────────────────┤
│ 2010-04-14 00:00:00 │ 12.6941,12.6941,12.6941,12.6941,12.3851,12.3851,12.3851,12.3851,,,,                         │
│ 2010-04-14 00:20:00 │ 12.389,12.389,12.389,12.389,12.1836,12.1836,12.1836,12.1836,11.3887,11.3887,11.3887,11.3887 │
└─────────────────────┴─────────────────────────────────────────────────────────────────────────────────────────────┘