Date history table

Question

I'm struggling with a basic query in Oracle and I'm having some trouble getting my head around it. Basically, the table is like this:
ID STATUS_DATE CLIENT_STATUS
1 12/10/2010 P
1 12/09/2010 C
1 12/03/2010 D
2 11/15/2010 E
2 11/16/2010 F
I want the query to return the max date and the most recent date group by ID. So the result should be for ID = 1 followed by 2.
ID CURRENT STATUS DATE PREVIOUS_STATUS_DATE CURRENT_STATUS PREVIOUS_STATUS
1 12/10/2010 12/09/2010 P C
2 11/16/2010 11/15/2010 F E
Basically, the query involves selecting Status_DATE Current_STATUS_DATE
ORDER BY STATUS_DATE
GROUP BY ID
--where each GROUP ID = 2
To clarify - I want the Max date of the Client ID group followed by the next date in order - only two rows but I want the results in one row.
The problem where I'm stumped over is trying to obtain the previous status and the previous status date..
Happy New Year!

Answer 1

Hi,
Welcome to the forum!
Use the analytic ROW_NUMBER function to number the rows of each id in descending order by status_date:
WITH     got_r_num     AS
     SELECT     id, status_date, client_status
     ,     ROW_NUMBER () OVER ( PARTITION BY  id
                         ORDER BY        status_date     DESC
                       )     AS r_num
     FROM     table_x
--     WHERE     ...     -- Any filtering goes here
SELECT       id
,       MIN (CASE WHEN r_num = 1 THEN status_date   END)     AS current_status_date
,       MIN (CASE WHEN r_num = 2 THEN status_date   END)     AS previous_status_date
,       MIN (CASE WHEN r_num = 1 THEN client_status END)     AS current_status
,       MIN (CASE WHEN r_num = 2 THEN client_status END)     AS previous_status
FROM       got_r_num
GROUP BY  id
;The main query is an example of a Pivot , where you display a column from multiple rows as multiple columns on one row. There's a better way to do it in Oracle 11, but you didn't say what version of Oracle you're using. As written, the query above will work in Oracle 9 (and up), and can be easily modified to run in Oracle 8.1.