Question

I’m an Android programmer, and I use SQLite (don’t have much choice 🙂 ) in my app.
I have a table, that contains a field of unix time stamp. Right now, if I want to make a sum of some field in this table, and group by months, I just do:

SELECT month, year, sum(x)
FROM foo
GROUP BY month, year

(Of course that the month and year are date functions).

But I want to group it by non calendar month, like from the 10th of one month, to the 10th that comes after him.

I have a very basic knowledge in SQL so I have no clue on how to do it.
Someone told me I need to use PARTITION BY but SQLite doesn’t support it.
I’m pretty sure there’s a way to do it.

Thanks in advance,
Elad

Answer 1

To handle the tenth of the month, you can just subtract that 10 days from the date:

select strftime("%y %m", tendaysbefore), <whatever>
from (select foo.*,
             date(thedate, '-10 days') as tendaysbefore
      from foo
     ) t
group by strftime("%Y-%m", tendaysbefore)
order by 1, 2

You can put the year and month into separate columns. This example has them in one column.