SELECT id, starts_at, ends_at, title
FROM yourtable
WHERE '2011-01-01' BETWEEN starts_at AND ends_at
OR '2011-05-01' BETWEEN starts_at AND ends_at
OR '2011-10-01' BETWEEN starts_at AND ends_at
SELECT id, starts_at, ends_at, title
FROM yourtable
WHERE '2011-01-01' BETWEEN starts_at AND ends_at
OR '2011-05-01' BETWEEN starts_at AND ends_at
OR '2011-10-01' BETWEEN starts_at AND ends_at