Cleaning up data

Question

I have to clean-up some data in an existing table, so we can move towards a cleaner design:
The data I currently have:
ID____Plan Name_____Effective Date_____End Date
1______Plan A_______ 01/01/2005_______NULL
2______Plan A_______05/02/2005________NULL
3______Plan A_______03/03/2006________NULL
4______Plan B_______01/02/2005________NULL
5______Plan B_______10/15/2005________NULL
6______Plan C_______01/01/2005________NULL
It is safe to assume the Effective end date will be in same incremental order as the ID.
When there is more than one instance of a Plan, I want to set the 'End Date' to 'Effective Date - 1' of the next record (identified by the ID). The End Date of the most recent record should remain NULL.
The result table should look like this:
ID____Plan Name_____Effective Date_____End Date
1______Plan A_______ 01/01/2005_______05/01/2005
2______Plan A_______05/02/2005________03/02/2006
3______Plan A_______03/03/2006________NULL
4______Plan B_______01/02/2005________10/14/2005
5______Plan B_______10/15/2005________NULL
6______Plan C_______01/01/2005________NULL
Anyway to do this?

Answer 1

Take your pick of methods. The first one requires that the next id = the previous id + 1, but the second one does not.
scott@ORA92> SELECT * FROM your_table
  2  /
        ID PLAN_NAME EFFECTIVE_DATE END_DATE
         1 Plan A    01/01/2005
         2 Plan A    05/02/2005
         3 Plan A    03/03/2006
         4 Plan B    01/02/2005
         5 Plan B    10/15/2005
         6 Plan C    01/01/2005
6 rows selected.
scott@ORA92> UPDATE your_table t
  2  SET    end_date =
  3           (SELECT effective_date - 1
  4            FROM   your_table
  5            WHERE  id = t.id + 1
  6            AND    plan_name = t.plan_name)
  7  /
6 rows updated.
scott@ORA92> SELECT * FROM your_table
  2  /
        ID PLAN_NAME EFFECTIVE_DATE END_DATE
         1 Plan A    01/01/2005     05/01/2005
         2 Plan A    05/02/2005     03/02/2006
         3 Plan A    03/03/2006
         4 Plan B    01/02/2005     10/14/2005
         5 Plan B    10/15/2005
         6 Plan C    01/01/2005
6 rows selected.
scott@ORA92> ROLLBACK
  2  /
Rollback complete.
scott@ORA92> UPDATE your_table t
  2  SET    end_date =
  3           (SELECT lead_date
  4            FROM   (SELECT id,
  5                     LEAD (effective_date) OVER
  6                       (PARTITION BY plan_name
  7                        ORDER BY id) - 1 AS lead_date
  8                 FROM   your_table)
  9            WHERE  id = t.id)
10  /
6 rows updated.
scott@ORA92> SELECT * FROM your_table
  2  /
        ID PLAN_NAME EFFECTIVE_DATE END_DATE
         1 Plan A    01/01/2005     05/01/2005
         2 Plan A    05/02/2005     03/02/2006
         3 Plan A    03/03/2006
         4 Plan B    01/02/2005     10/14/2005
         5 Plan B    10/15/2005
         6 Plan C    01/01/2005
6 rows selected.
scott@ORA92>