数据库 随机 提取 N条记录

随机取出n条记录：

mysql:

    Select * From tablename order By rand() Limit n 

SqlServer:

    select top n * from tablename order by newid()

Access:

    Select top n * FROM tablename orDER BY Rnd(id)

Oracle：

    Select * from (select * from tablename order by sys_guid()) where rownum < n
    Select * from (select * from tablename order by dbms_random.value) where rownum < n

DB2:

    Select * from tablename order by rand() fetch first n rows only