SQL query to bring months that doesn't exist in a column - mysql

Question

I want to count the number of rows with respect to the month that they've written in database. My database has a column named created_date. you can see what i've done bellow :
select month(created_date) as "Month", count(created_date) as "Count" from transactions group by month(created_date)
what this query returns is something like this :
{'Month':1,'Count':10}
this happens because i only have one month in my database, while i need to have all months in results, including months that doesn't exist in database, like this :
{'Month':1,'Count':10}
{'Month':2,'Count':0}
{'Month':3,'Count':0}
{'Month':4,'Count':0}
{'Month':5,'Count':0}
{'Month':6,'Count':0}
{'Month':7,'Count':0}
{'Month':8,'Count':0}
{'Month':9,'Count':0}
{'Month':10,'Count':0}
{'Month':11,'Count':0}
{'Month':12,'Count':0}
how should i do it?

Answer 1

You could JOIN to a list of months so you can get a row even for months that don't exist in your table:
SELECT m.month,
COUNT(t.created_date)
FROM (SELECT 1 AS month UNION ALL SELECT 2 UNION ALL SELECT 3
UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6
UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9
UNION ALL SELECT 10 UNION ALL SELECT 11 UNION ALL SELECT 12) m
LEFT JOIN transactions t ON MONTH(t.created_date) = m.month
GROUP BY m.month

Answer 2

SELECT * from
(
SELECT 1 as month UNION ALL
SELECT 2 as month UNION ALL
..
SELECT 12 as month
) as months
left outer join
(
select month(created_date) as "Month", count(created_date) as "Count" from transactions group by month(created_date)
) as data
on (months.month=data.month)
ORDER BY months.month