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Discover how to effectively set the values of dependent select lists in Oracle APEX, ensuring proper relationship between parent and child lists.
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Setting Values in Dependent Select Lists using Oracle APEX

When working with Oracle APEX, you may encounter situations where you have two select lists, where one (List A) acts as the parent and the other (List B) serves as the child. The challenge arises when trying to programmatically set the values of these lists in a manner that correctly respects their dependencies. If you've been facing issues with setting values in your dependent select lists, you’re not alone. This post will guide you through the steps needed to properly set the values of these lists to ensure they function seamlessly together.

Understanding the Problem

In our scenario:

List A (the parent) influences the values available in List B (the child).

When a user selects an option in List A, List B should refresh to reflect appropriate values based on the parent selection.

The issue lies when values are set via PL/SQL: List B shows null instead of the expected value, even though the options available in List B are limited to the ones associated with the selected value in List A.

Example Scenario

Desired Outcome: When IT is selected in List A, List B should show employees in that department, and upon setting them, John should be selected in List B.

Actual Outcome: Although IT is selected in List A, List B returns a null value, indicating a problem with how the values are being set.

The Solution

To address this issue, you need to separate the assignment of values between the parent and child lists in your Dynamic Action (DA). Here’s how:

Step-by-Step Guide

Creating Dynamic Action for Parent and Child

In your Oracle APEX application, navigate to the page with your select lists.

Create a Dynamic Action that triggers upon an event (like a button click).

Setting Up PL/SQL for the Parent List

Include a PL/SQL action in your Dynamic Action that assigns the selected value to List A.

Make sure to add the correct return items for this action, so APEX knows which values are being set.

Setting Up PL/SQL for the Child List

Immediately after the parent assignments, create a second PL/SQL action within the same Dynamic Action.

This action should take care of assigning the value to List B.

Why Separate Actions Work

This two-step process works because it allows the application to clearly understand the relationship and value dependencies between the two lists:

Separation Ensures Clarity: By processing the assignments in two distinct actions, APEX can refresh List B based on the newly selected option in List A before any value is assigned.

Avoiding Conflicts: Assigning both simultaneously may lead APEX to treat them as a static assignment, confusing the expected data refresh.

Testing the Implementation

After implementing these changes:

Run your application and select a value in List A.

Confirm if List B is appropriately updated based on the selection.

Check if you can set the intended values correctly: List A as IT and List B as John.

Conclusion

By separating the PL/SQL assignments into two distinct actions within your Dynamic Action, you can successfully manage the relationship between dependent select lists in Oracle APEX. This method ensures that List B retrieves and displays the correct values based on the selection made in List A.

If you continue to encounter issues or have further questions regarding this process, feel free to reach out for more technical assistance!