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postgresqltime-seriesaggregatetimeserieschart
Greg Olsen
Greg Olsen

Reputation: 1380

Postgresql Time Series for each Record

I'm having issues trying to wrap my head around how to extract some time series stats from my Postgres DB.

For example, I have several stores. I record how many sales each store made each day in a table that looks like:

+------------+----------+-------+
|    Date    | Store ID | Count |
+------------+----------+-------+
| 2017-02-01 |        1 |    10 |
| 2017-02-01 |        2 |    20 |
| 2017-02-03 |        1 |    11 |
| 2017-02-03 |        2 |    21 |
| 2017-02-04 |        3 |    30 |
+------------+----------+-------+

I'm trying to display this data on a bar/line graph with different lines per Store and the blank dates filled in with 0.

I have been successful getting it to show the sum per day (combining all the stores into one sum) using generate_series, but I can't figure out how to separate it out so each store has a value for each day... the result being something like:

["Store ID 1", 10, 0, 11,  0]
["Store ID 2", 20, 0, 21,  0]
["Store ID 3",  0, 0,  0, 30]

Upvotes: 1

Views: 197

Answers (1)

Clodoaldo Neto
Clodoaldo Neto

Reputation: 125244

It is necessary to build a cross join dates X stores:

select store_id, array_agg(total order by date) as total
from (
    select store_id, date, coalesce(sum(total), 0) as total
    from
        t
        right join (
            generate_series(
                (select min(date) from t),
                (select max(date) from t),
                '1 day'
            ) gs (date)
            cross join
            (select distinct store_id from t) s
        ) using (date, store_id)
    group by 1,2
) s
group by 1
order by 1
;
 store_id |    total    
----------+-------------
        1 | {10,0,11,0}
        2 | {20,0,21,0}
        3 | {0,0,0,30}

Sample data:

create table t (date date, store_id int, total int);
insert into t (date, store_id, total) values
('2017-02-01',1,10),
('2017-02-01',2,20),
('2017-02-03',1,11),
('2017-02-03',2,21),
('2017-02-04',3,30);

Upvotes: 2

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