SQL Server--> SELECT TOP 50 * FROM TAB_USERS ORDER BY NEWID();

ORACLE--> SELECT * FROM (SELECT * FROM TAB_USERS ORDER BY DBMS_RANDOM.RANDOM()) WHERE RONUM<=50

MYSQL--> SELECT * FROM TAB_USERS ORDER BY RAND() LIMIT 50

{

ACCESS--> SELECT TOP 50 * FROM TAB_USERS ORDER BY RND([字段])

这条语句在ACCESS中的查询结果是正确的，但在等后台代码要写成如下：

Random random=new Random(System.Guid.NewGuid().GetHashCode());

int val=random.Next();

string sql="SELECT TOP 50 * FROM TAB_USERS ORDER BY RND("+(-r)+"字段)";

}