mysql随机获取数据

SELECT * FROM users  AS t1  JOIN (SELECT ROUND(RAND() * ((SELECT MAX(userId) FROM `users`)-(SELECT MIN(userId) FROM users))+(SELECT MIN(userId) FROM users)) AS userId) AS t2 WHERE t1.userId >= t2.userId ORDER BY t1.userId LIMIT 1

		

SELECT * FROM users WHERE userId >= ((SELECT MAX(userId) FROM users)-(SELECT MIN(userId) FROM users)) * RAND() + (SELECT MIN(userId) FROM users)  LIMIT 1