sql - Postgresql group month wise with missing values

Question

first an example of my table:

id_object;time;value;status
1;2014-05-22 09:30:00;1234;1
1;2014-05-22 09:31:00;2341;2
1;2014-05-22 09:32:00;1234;1
...
1;2014-06-01 00:00:00;4321;1
...

Now i need count all rows with status=1 and id_object=1 monthwise for example. this is my query:

SELECT COUNT(*)
FROM my_table
WHERE id_object=1
  AND status=1
  AND extract(YEAR FROM time)=2014
GROUP BY extract(MONTH FROM time)

The result for this example is:

2
1

2 for may and 1 for june but i need a output with all 12 months, also months with no data. for this example i need this ouput:

0 0 0 0 2 1 0 0 0 0 0 0

Thx for help.

Answer 1

you can use generate_series() function like this:

select
    g.month,
    count(m)
from generate_series(1, 12) as g(month)
    left outer join my_table as m on
        m.id_object = 1 and
        m.status = 1 and
        extract(year from m.time) = 2014 and
        extract(month from m.time) = g.month
group by g.month
order by g.month

sql fiddle demo