数据处理Row_Number（）SQL Server

Question

I need some guidance and help with a data manipulation question in SQL SERVER 2012.

This is how my data looks like:

=================================================
YearMonth LocationCode  New     ValidTo
=================================================
201412         2020     1       201502
201501        2020      1       201503
201503        3030      1       201506
201506        3030      1       201509

Problem description

if you look at the above table, you will see the column YearMonth , locationCode , New which tells whether the locationCode is new for the month in the row. The ValidTo column shows to which ValidTo YearMonth it is validto.

For the example, for YearMonth 201412, the locationCode 2020 is 1, which means here it is New and that LocationCode is considered New till ValidTo 201502.

My problem is that I need to make each LocationCode , that appears in the earliest YearMonth Column, to New, is this case "1" till the ValidTo YearMonth.

Objective:

=================================================
YearMonth LocationCode  New     ValidTo
=================================================
201412         2020     1       201502
201501        2020      1       201503
201503        3030      1       201506
201506        3030      0       201509

Basically, I need to find out the MIN() for each LocationCode and then categorize it as NEW ,"1" and if the LocationCode appears within the MIN() YearMonth and ValidTo then categorize the LocationCode in New as "1".

How Can I do that? The above table provides a visual example.

I have edited my final table to make it simpler to understand my question.

Basically,the MIN() Year for LocationCode 3030 is 201503 and the LocationCode is valid till 201506 as demostrated in the Validto Column. If the LocationCode 3030 were to appear in the YearMonth row, 201505 with a VALIDTO till 201506, then we classify it as New (1) as well.

Basically,pseudocode

SELECT

MIN(YearMonth),
LocationCode

from Tabl

If LocationCode , is in MIN(YearMonth) AND ValidTO timeperiod then classify it as 1. How can I do this?

Answer 1

Please try the below query for updating the table: The inner most query calculates the minimum Yearmonth per LocationCode which is used to calculate all ValidTo and LocationCode s which need to be updated to 1 in ValidTo column

update t2
set New= CASE when t1.ValidTo is null then 0 else 1 end 
FROM tbl t2
LEFT JOIN 
(
  select t.ValidTo, t.locationCode 
       from tbl t inner join
           (
             select 
                MIN(YearMonth) as MYM, 
                LocationCode 
             from tbl
               group by LocationCode
            ) g 
       on t.YearMonth=g.MYM and t.LocationCode=g.LocationCode
) t1
on t2.ValidTo=t1.ValidTo and t2.LocationCode=t1.LocationCode

sample sql fiddle for demo: http://sqlfiddle.com/#!6/229d8