select top 10 * from tb where DATEPART(weekday,LoginTime) in(6,7) order by LoginTime  desc

------解决方案--------------------
SQL code
select
 distinct b.* 
from
 tb a 
cross apply
(select top 10 * from tb where LoginTime=a.LoginTime and DATEPART(weekday,LoginTime) in(6,7) order by LoginTime  desc)b

------解决方案--------------------
你有什么辅助信息可以查到哪天对应的是星期几吗？如果没有，可以使用以下方法获取某天是星期几：
SQL code
select DATENAME(WEEKDAY,@Date) AS '本日是周几'  
select DATEPART(WEEKDAY,@Date) AS '本日是周几'--返回值 1-星期日，2-星期一，3-星期二......7-星期六

------解决方案--------------------
SQL code

select top 10 loginIP,loginTime from 表
where datepart(weekday,loginTime)=6 or datepart(weekday,loginTime)=7