All Months This Year Containing Events (TEC)

-- We are only interested in months
SELECT DISTINCT SUBSTR(meta_value, 6, 2)
FROM wp_postmeta

-- Where the event starts this year
WHERE meta_key = '_EventStartDate'
AND meta_value > '2012-01-01 00:00:00'
AND meta_value < '2012-12-31 23:59:59'

-- List them in ascending order
ORDER BY `meta_value` ASC;