Get all numbers 1-100 per ID even without data - sql

Question

I have a table which looks like this:
ID
money_earned
days_since_start
1
1000
1
1
2000
2
1
3000
4
1
2000
5
2
1000
1
2
100
3
I want that rows, without a days_since_start (which means that the money_earned column was empty that day) - will include all the days PER ID, with "money" being null to indicate there was no earnings, so it to look like this:
ID
money_earned
days_since_start
1
1000
1
1
2000
2
1
NULL
3
1
3000
4
1
2000
5
2
1000
1
1
NULL
2
2
100
3
I have tried to look up for something like that, but I don't even know what function does that...
thank you!

Answer 1

You can first generate table for your ids and days by query
SELECT d1.id, generate_series(1, max(d1.days_since_start)) AS days_since_start
FROM days d1 JOIN days d2 ON d1.id = d2.id GROUP BY d1.id
(if you need all numbers from 1 to 100, you can replase exspression max(d1.days_since_start) with the number 100)
and then join it with your table. the final query might look like this
WITH genDays AS
(SELECT d1.id, generate_series(1, max(d1.days_since_start)) AS days_since_start
FROM days d1 JOIN days d2 ON d1.id = d2.id GROUP BY d1.id)
SELECT coalesce(genDays.id, d3.id) AS id,
d3.money_earned,
coalesce(d3.days_since_start, genDays.days_since_start) AS days_since_start
FROM days d3 FULL JOIN genDays ON genDays.id = d3.id
AND genDays.days_since_start = d3.days_since_start
the output will be as you need
if you need to fill the nulls with last nonnull value per id then you can modify the query like here
WITH genDays AS
(SELECT d1.id as id, generate_series(1, 100) AS days_since_start
FROM days d1 JOIN days d2 ON d1.id = d2.id GROUP BY d1.id)
SELECT coalesce(genDays.id, d3.id) AS id,
coalesce(d3.money_earned,
(
select d4.money_earned
from days d4
where d4.id = genDays.id
and d4.days_since_start < genDays.days_since_start
order by d4.days_since_start desc
limit 1
)) as money_earned,
coalesce(d3.days_since_start, genDays.days_since_start) AS days_since_start
FROM days d3 FULL JOIN genDays ON genDays.id = d3.id
AND genDays.days_since_start = d3.days_since_start