Question

I have this MySql query:

SELECT YEAR(date), MONTHNAME(date), SUM(block_time)
FROM flights
WHERE operator = 'PSD'
GROUP BY YEAR(date), MONTH(date)

The problem I am having is if a month has zero hours it doesn’t appear in the results. What do I need to change in order to see all months whether or not there is any time flown that month?

Answer 1

You need a table including all the years / months your want in your results, and would need to join it as below…

SELECT myMonths.theYear, myMonths.theMonth, COALESCE(theData.hours, 0)
FROM myMonths
LEFT JOIN (
    SELECT YEAR(date) AS theYear, MONTHNAME(date) AS theMonth, SUM(block_time) AS hours
    FROM flights
    WHERE operator = 'PSD'
    GROUP BY YEAR(date), MONTHNAME(date)
) theData
ON myMonths.theYear = theData.theYear
AND myMonths.theMonth = theData.theMonth