mysql 随机取数据
SELECT t1.id as id,title,content,class_name,class_id,hits FROM table AS t1
JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM table)-(SELECT MIN(id) FROM table ))+(SELECT MIN(id) FROM table)) AS id) AS t2
WHERE t1.id >= t2.id ORDER BY t1.id LIMIT 1;
