您应该将此表与1..12表保持联接。像这样的东西：
SELECT Months.id AS `month` ,
COUNT(`reports`.date_lm) AS `count`
FROM
(
SELECT 1 as ID UNION SELECT 2 as ID UNION SELECT 3 as ID UNION SELECT 4 as ID
UNION
SELECT 5 as ID UNION SELECT 6 as ID UNION SELECT 7 as ID UNION SELECT 8 as ID
UNION
SELECT 9 as ID UNION SELECT 10 as ID UNION SELECT 11 as ID UNION SELECT 12 as ID
) as Months
LEFT JOIN `reports` on Months.id=month(`reports`.date_lm)
AND
(status = 'submitted')
AND (date_lm > 2012-08)
GROUP BY Months.id
ORDER BY Months.id ASC
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