Finding payday changes in credit cards

Question

Hi gurus
We grant credit cards to customers and each customer has a payday.
We want to know how many times customers change their payday and their balance at that moment.
Here an example for a customer:
YearMonth Payday Balance
201001 10     1000
201002 10     1600
201003 10     1400
201004 20     1500
201005 20     2000
201006 20     1800
201007 20     1600
201008 20     3000
201009 20     2500
201010 10     2400
201011 10     2100
201012 10     2000
I want to build a single sql sentence that return just this records:
YearMonth Payday Balance
201004 20     1500
201010 10     2400
Can this be possible?
Thanks in advance
Oscar

Answer 1

It looks like you want something like
SELECT *
  FROM (
    SELECT YearMonth,
           Payday,
           Balance,
           lag(Payday) over (order by YearMonth) priorPayday
      FROM some_table_name )
WHERE payday != priorPaydayFrom a data model standpoint, though, you'd be much better off if YearMonth was a DATE column rather than what I hope is a NUMBER column.
Justin