从数据库里随机读取几条数据

从数据库里随机读取几条数据
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:
select * from table order by dbms_random.value()