Question

I have a table which has columns UserID,DIFFTIME. when I select these columns from the table, I also want to have a derived column which is : If the DiffTime is > 20 I want to increment the count per user id.

For example if the table has:

User ID DIFF TIME
 1        0
 1        5
 1        10
 2        0
 2        21
 2        5 

I want a result set that is something like this:

User ID DIFF TIME SESSION NUMBER
     1        0        1
     1        5        1
     1        10       1
     2        0        1
     2        21       2
     2        5        2

How do I accomplish this.

Ideas and suggestions are much appreciated!

Answer 1

create table #t
(
 id int,
 Diff int,
 SessionNumber int
)
insert into #t(id, diff)values(1, 0)
insert into #t(id, diff)values(1, 5)
insert into #t(id, diff)values(1, 10)
insert into #t(id, diff)values(2, 0)
insert into #t(id, diff)values(2, 21)
insert into #t(id, diff)values(2, 5)


Select ROW_NUMBER() over(order by Id) as RowID, * into #Temp1 from #t 
Declare @diff int
Declare @RowId int
Declare @Previous int
Declare @NewValue int

DECLARE @Cur CURSOR SET @Cur = CURSOR FOR select RowId, diff from #Temp1
OPEN @Cur
FETCH NEXT FROM @Cur INTO @RowId, @diff
WHILE @@FETCH_STATUS = 0
BEGIN
    if(@RowId = 1)
    Begin
        Update #Temp1 Set SessionNumber = 1 Where rowid = 1     
        Set @Previous = @Diff
        Set @NewValue = 1
    End
    Else
    Begin
        if(@Diff - @Previous > 20)
        Begin
            Set @Previous = @Diff
            Set @NewValue = @NewValue + 1
            Update #Temp1 Set SessionNumber = @NewValue Where rowid = @RowId
        End
        else
            Update #Temp1 Set SessionNumber = @NewValue Where rowid = @RowId

    End
    FETCH NEXT FROM @Cur INTO @RowId, @diff
END
CLOSE @Cur
DEALLOCATE @Cur

select * from #temp1

drop table #t
drop table #temp1