How to implement subquery in OWB mapping

Question

I am trying to build a mapping (OWB 10gR2) which uses a single driver table (COLLEGE) and requires additional columns from 2 other tables (CONTACT and DEMOGRAPHIC) which have a many-to-one relationship with the driver table. The output should be a single record for each record in the driver table.
For the join to the CONTACT table I only want to return the first record found. The join for the DEMOGRAPHIC table should return the record with the MAXIMUM year. In SQL I would handle these relationships via subqueries. Here is a sample of the SQL that I would use:
select college_CODE,
college_DESC,
contact_NAME,
contact_PTYP_CODE,
demographic_DEMO_YEAR,
demographic_CALENDAR_TYPE,
demographic_ACCREDITATION_TYPE
from college, contact, demographic
where college_code = contact_sbgI_code
AND contact.ROWID = (SELECT MIN(A.contact.ROWID)
FROM contact A
WHERE A.contact_SBGI_CODE = college.college_CODE )
AND college.college_CODE = demographic.demographic_SBGI_CODE
And demographic.demographic_DEMO_YEAR = (SELECT MAX(B.demographic_DEMO_YEAR)
FROM demographic B
WHERE B.demographic_SBGI_CODE = college.college_CODE)
How do I implement this logic within OWB? Is there any way to do it without using views?
Thank you in advance!
Chuck

Answer 1

Hi,
Try this way....join college and contact tables (if u r maintaining history in contact table use the dates also to join) and get the min of effective date form the contact table thru the aggregator...this will give u the first record....then join the result with the DEMOGRAPHIC table and get use the aggregator to get max of the year...this should give u the right result...
Regards
Bharath