oracle、my sql、sql随机查询语句

1. Oracle,随机查询20条 select * from( select * from 表名 order by dbms_random.value) where rownum <= 20; 2.SQL Server，随机查询20条 select top 20 * from 表名order by newid() 3.My SQL:，随机查询20条 select * from 表名 order by rand() limit 20