Access: select top n * from table order by rnd(id)‘id为数据库的自动编号字段
Sql Server: select top n * from table order by newid()
MySQL:
SELECT * FROM table order by rand() limit 20;
Oracle:
从数据库里随机读取几条数据
原文：http://www.cnblogs.com/chenmfly/p/4404439.html
