去重SQL

转载 ：http://www.jb51.net/article/129656.htm

DELETE re_question_verify 
FROM
	re_question_verify,
	(
SELECT
	min(id) id,
	question_id,
	verify_id
FROM
	re_question_verify 
GROUP BY
	question_id,
	verify_id
HAVING
	count(*) > 1 
	) t2 
WHERE
	re_question_verify.question_id = t2.question_id 
	AND re_question_verify.verify_id = t2.verify_id 
	AND re_question_verify.id > t2.id;