Derived Column for "PATH"

Question

I have a table with the first 3 colums below. Is there a way to generate the fourth column? I need to string together the location by date (asc). if the location does not change, then I do not string the data. There should be one path per ID. I have tried using window functions but can't seem to figure it out. I also cannot use P/SQL for this. It needs to be regular SQL. The following is sample data.
ID DATE Location PATH
A 01/01/2006 CA CA
A 01/02/2006 CA CA
A 01/10/2006 CA CA
B 01/01/2006 CA CA-TX-CA
B 01/02/2006 TX CA-TX-CA
B 01/10/2006 CA CA-TX-CA
C 01/01/2006 CA CA-NY-CA-TX
C 01/02/2006 CA CA-NY-CA-TX
C 01/10/2006 NY CA-NY-CA-TX
C 01/01/2006 CA CA-NY-CA-TX
C 01/02/2006 CA CA-NY-CA-TX
C 01/10/2006 TX CA-NY-CA-TX
I would greatly appreciate any help on this,
Sam

Answer 1

Try this (not tested)
SELECT id,
       LTRIM(MAX(SYS_CONNECT_BY_PATH(location,'-'))
       KEEP (DENSE_RANK LAST ORDER BY curr),'-') AS path
FROM   (SELECT id,
               location
               ROW_NUMBER() OVER (PARTITION BY id ORDER BY date) AS curr,
               ROW_NUMBER() OVER (PARTITION BY id ORDER BY date) -1 AS prev
        FROM   <your_table>)
GROUP BY id
CONNECT BY prev = PRIOR curr AND id = PRIOR id
START WITH curr = 1;For other string aggregation techniques see
http://www.oracle-base.com/articles/10g/StringAggregationTechniques.php