选择忽略一个字段的不同值

Question

I have a table similar to this

Table(Id int, PropertyId int, UserId int, AccesedOn datetime)

So the table can have value for one property for one user, but different times.

Eg.
1,100,5, 2012-10-16 16:24:48
2,100,5, 2012-10-17 11:22:00
3,100,5, 2012-10-18 17:10:05

What I am trying here is to select distinct properties for specific user, but order by most recent access time.

Also I am joining this table to three other tables which result in providing duplicate values. Therefore I have to use DISTINCT command.

Problem I have is since I doing the orderby AccesedOn , it need to appear on select statement which doesn't brings the distinct values since the AccesedOn column have different values.

For above example it should return only 3,100,5, 2012-10-18 17:10:05

Any suggestions to overcome this?

Answer 1

;WITH CTE as(
select *,ROW_NUMBER() over (partition by PropertyId,UserId  order by AccesedOn desc) as rn
from table1)

select * from CTE where rn=1

Answer 2

It is more likely that you need a subselect than that you need a distinct for this.

select * 
from Table A
where AccessedOn in
  (Select max(AccessedOn) from table B where A.UserId = B.UserId)

Answer 3

Instead of using DISTINCT , you can use MAX() and group by the rest of the columns

Select Id, PropertyId, UserId, MAX(AccesedOn)
From Table t
group by Id, PropertyId, UserId

This should give you the results you are looking for.