Populating LOVs Dynamically Using Record Groups in Oracle Forms

In Oracle Forms, List of Values (LOVs) provide users with a convenient way to select valid values for form fields. While static LOVs are easy to create, there are many situations where the list of values needs to change dynamically based on conditions, queries, or user input. This is where Record Groups come into play.

This article will guide you through the process of populating LOVs dynamically using Record Groups in Oracle Forms, explain the built-in procedures involved, and provide practical examples to help you implement them effectively.

What are Record Groups in Oracle Forms?

A Record Group is an in-memory data structure in Oracle Forms that acts like a query result set. You can create it at design time or dynamically at runtime using PL/SQL.

Record Groups are commonly used to populate LOVs, making them dynamic and flexible. Instead of hardcoding queries in an LOV, you can build and modify them on the fly, ensuring that users always see the most relevant data.

Why Use Record Groups for LOVs?

Using Record Groups allows developers to:

• Control LOV content dynamically based on user input or application context.
• Reuse LOVs across different parts of the form with different queries.
• Improve performance by restricting data in LOVs to only what’s needed.
• Enhance flexibility by building LOVs for multiple scenarios without creating separate objects.

Built-in Procedures for Record Groups

To work with Record Groups and LOVs, Oracle Forms provides several built-in procedures:

1. CREATE_GROUP_FROM_QUERY
   Creates a record group dynamically based on a SQL query.
2. POPULATE_GROUP
   Executes the query and fills the record group with data.
3. DELETE_GROUP
   Removes a record group from memory.
4. POPULATE_GROUP_WITH_QUERY
   Refreshes an existing group with a new query.
5. SHOW_LOV
   Displays the LOV associated with a record group.

Steps to Populate LOVs Dynamically

Here’s a step-by-step approach to creating and populating LOVs dynamically using record groups:

1. Define an LOV Object

• In Object Navigator, create an LOV.
• Initially, associate it with a dummy record group.
• This LOV will later be linked to a dynamically created record group.

2. Write a Dynamic Query for Record Group

Use CREATE_GROUP_FROM_QUERY to define the record group with a SQL statement. Example:

DECLARE
   rg_id   RecordGroup;
   rg_name VARCHAR2(30) := 'DEPT_RG';
   lov_id  LOV;
   ret     NUMBER;
BEGIN
   rg_id := FIND_GROUP(rg_name);

   -- If group already exists, delete it
   IF NOT ID_NULL(rg_id) THEN
      DELETE_GROUP(rg_id);
   END IF;

   -- Create new record group with query
   rg_id := CREATE_GROUP_FROM_QUERY(rg_name,
             'SELECT DEPTNO, DNAME FROM DEPT ORDER BY DNAME');

   -- Populate the group
   ret := POPULATE_GROUP(rg_id);

   -- Attach group to LOV
   lov_id := FIND_LOV('DEPT_LOV');
   SET_LOV_PROPERTY(lov_id, GROUP_NAME, rg_name);

   -- Show the LOV
   SHOW_LOV('DEPT_LOV');
END;

3. Attach the LOV to a Field

• In the Property Palette of the target text item (e.g., EMP.DEPTNO), assign the LOV created.
• The LOV will display dynamically based on the record group.

Example: LOV Based on User Input

Suppose you want to display employees for a selected department:

DECLARE
   rg_id   RecordGroup;
   rg_name VARCHAR2(30) := 'EMP_RG';
   lov_id  LOV;
   ret     NUMBER;
   v_dept  NUMBER := :EMP.DEPTNO;
BEGIN
   rg_id := FIND_GROUP(rg_name);

   IF NOT ID_NULL(rg_id) THEN
      DELETE_GROUP(rg_id);
   END IF;

   rg_id := CREATE_GROUP_FROM_QUERY(rg_name,
             'SELECT EMPNO, ENAME FROM EMP WHERE DEPTNO = ' || v_dept);

   ret := POPULATE_GROUP(rg_id);

   lov_id := FIND_LOV('EMP_LOV');
   SET_LOV_PROPERTY(lov_id, GROUP_NAME, rg_name);

   SHOW_LOV('EMP_LOV');
END;

Here, the LOV will only display employees belonging to the department entered by the user.

Best Practices for Dynamic LOVs

1. Always check if a record group exists before creating a new one.
2. Delete old record groups to prevent memory issues.
3. Validate user input before using it in queries to avoid runtime errors.
4. Limit rows in dynamic LOVs for better performance.
5. Reuse LOV objects by simply reassigning different record groups.

Conclusion

Using Record Groups to populate LOVs dynamically in Oracle Forms is one of the most effective ways to build flexible and responsive applications. Instead of static queries, you can create LOVs that adjust based on user input, context, or business rules. By leveraging built-in procedures like CREATE_GROUP_FROM_QUERY, POPULATE_GROUP, and SHOW_LOV, developers can deliver more intelligent and user-friendly Oracle Forms applications.