sqlsever中使用的 select top n在mysql 语句中如何更改

string sqlSelect = "select top(3) ROW_NUMBER() over(order by UserTime) as Num,* from " + "UserScore1";

改后

 string sqlSelect = "select a.UserName,a.UserTime as Num from userscore1 a ORDER BY a.UserTime LIMIT 3";

用的Limit