gistfile1.sql

# All posts tagged with tag 1 AND tag 2

# The two on the right side of the condition should match the number of tags you need to match on.
# If it was three tags, it would be = 3.

SELECT *
FROM `posts`
WHERE (
	SELECT COUNT(1)
	FROM `postTags`
	WHERE
		postTag_post_id = post_id AND
		postTag_tag_id IN (1, 2)
) = 2;