Question

I m trying to achieve flag setting for the condition in my table below

p_id      mon_year      e_id     flag  
----      ---------     -----    -----
 1          2011/11       20       0
 1          2011/11       21       1
 1          2012/01       22       1
 1          2012/02       23       0
 1          2012/02       24       0
 1          2012/02       25       1
 2          2011/11       28       0
 2          2011/11       29       1
 2          2012/01       30       1

grouping by p_id,e_id and mon_year, the flag is set for the last value in the month.

I m confused how can i achieve this

I tried to achieved this by using row_number and partition to seperate out the value. By still looking for to achieved

Output by using row_number query , i have got is as below:

Grouping by

p_id      mon_year      e_id     row
----      ---------     -----    -----
 1          2011/11       20       1
 1          2011/11       21       2
 1          2012/01       22       1
 1          2012/02       23       1
 1          2012/02       24       2
 1          2012/02       25       3
 2          2011/11       28       1
 2          2011/11       29       2
 2          2012/01       30       1

Max of this value would set the flag column. But i m really bugged how to achieve it. Any help would be useful.

Thanks !!

Answer 1

I think this is what you’re going for. . . The output exactly matches your example:

declare @t table (p_id int, [year] int, [month] int,  [day] int)
insert @t select 1, 2011, 11, 20
    union select 1, 2011, 11, 21
    union select 1, 2012, 01, 22
    union select 1, 2012, 02, 23
    union select 1, 2012, 02, 24
    union select 1, 2012, 02, 25
    union select 2, 2011, 11, 28
    union select 2, 2011, 11, 29
    union select 2, 2012, 01, 30

select p_id, [year], [month], [day] 
, case when r=1 then 1 else 0 end flag
from
(
    select p_id, [year], [month], [day]
    , row_number() over (partition by p_id, [year], [month] order by [day] desc) r
    from @t
) x
order by  p_id, [year], [month], [day]

Output:

p_id    year    month   day     flag
1       2011    11      20      0
1       2011    11      21      1
1       2012    1       22      1
1       2012    2       23      0
1       2012    2       24      0
1       2012    2       25      1
2       2011    11      28      0
2       2011    11      29      1
2       2012    1       30      1