Using Post_Query Trigger in Oracle Forms

When a query is open in the block, the Post-Query trigger fires each time Form Builder fetches a record into a block. The trigger fires once for each record placed on the block’s list of records. 

Usage Notes
Use a Post-Query trigger to perform the following tasks:
·  populate control items or items in other blocks
·  calculate statistics about the records retrieved by a query
·  calculate a running total
·  When you use a Post-Query trigger to SELECT non-base table values into control items, Form Builder marks each record as CHANGED, and so fires the When-Validate-Item trigger by default. You can avoid the execution of the When-Validate-Item trigger by explicitly setting the Status property of each record to  QUERY in the Post-Query trigger. To set record status programmatically, use SET_RECORD_PROPERTY. 

See also:
http://www.foxinfotech.in/2013/02/populating-display-item-value-on-query.html
http://www.foxinfotech.in/2014/02/pre-query-post-query-displayitem-oracle-forms.html
Example
This example retrieves descriptions for code fields, for display in non-database items in the current block.
DECLARE
CURSOR lookup_payplan IS SELECT Payplan_Desc
FROM Payplan
WHERE Payplan_Id =
:Employee.Payplan_Id;
CURSOR lookup_area IS SELECT Area_Name
FROM Zip_Code
WHERE Zip = :Employee.Zip;
BEGIN
/*
Lookup the Payment Plan Description given the Payplan_Id in the Employee Record just fetched. Use Explicit Cursor for highest efficiency.
*/
OPEN lookup_payplan;
FETCH lookup_payplan INTO :Employee.Payplan_Desc_Nondb;
CLOSE lookup_payplan;
/*
Lookup Area Descript given the Zipcode in the Employee Record just fetched. Use Explicit Cursor for highest efficiency.
*/
OPEN lookup_area;
FETCH lookup_area INTO :Employee.Area_Desc_Nondb;
CLOSE lookup_area;
END;