SQL query: Fill missing values with 0 - sql

Question

I have a table with gaps in data at certain times (see there is no data between 37 & 46). I need to fill in those gaps with 0 for better display on the frontend.
date | mydata
--------+-----------------
911130 | 10
911131 | 11
911132 | 9
911133 | 6
911134 | 5
911135 | 5
911136 | 10
911137 | 8
911146 | 4
911147 | 5
911148 | 9
911149 | 14
911150 | 8
The times are sequential integers (UNIX timestamps initially). I have aggregated my data into 5 minute time buckets.
The frontend query will pass in a start & end time and aggregate the data into larger buckets. For example:
SELECT
(five_min_time / 6) AS date,
SUM(mydata) AS mydata
FROM mydata_table_five_min
WHERE
five_min_time BETWEEN (1640000000 / 300) AND (1640086400 / 300)
GROUP BY date
ORDER BY date ASC;
I would like to be able to get a result:
date | mydata
--------+-----------------
911130 | 10
911131 | 11
911132 | 9
911133 | 6
911134 | 5
911135 | 5
911136 | 10
911137 | 8
911138 | 0
911139 | 0
911140 | 0
911141 | 0
911142 | 0
911143 | 0
911144 | 0
911145 | 0
911146 | 4
911147 | 5
911148 | 9
911149 | 14
911150 | 8
As a note, this query is being run in AWS Redshift.

Answer 1

Not sure if a recursive CTE works in redshift.
But something like this works in postgresql.
with recursive rcte as (
select
min(half_hour) as n,
max(half_hour) as n_max
from cte_data
union all
select n+1, n_max
from rcte
where n < n_max
)
, cte_data as (
select
(five_min_time / 6) as half_hour,
sum(mydata) as mydata
from mydata_table_five_min
where five_min_time between (date_part('epoch','2021-12-20 12:00'::date)::int / 300)
and (date_part('epoch','2021-12-21 12:00'::date)::int / 300)
group by half_hour
)
select n as date
--, to_timestamp(n*6*300) as dt
, coalesce(t.mydata, 0) as mydata
from rcte c
left join cte_data t
on t.half_hour = c.n
order by date;