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Dynamic LOV Selection Based on Item - Oracle APEX

In modern business applications, role-based input restrictions are common. For example:

  • Certain users can select only a limited number of options in multi-select fields.
  • Others have no restriction.
  • Sometimes, selection depends on another field value, like a designation.

Implementing such dynamic validations in Oracle APEX can be done efficiently using JavaScript functions combined with Dynamic Actions, keeping logic reusable and maintainable.

Key Components

  • Global Validation Function: A single JavaScript function that validates any multi-select LOV based on a controlling field (e.g., designation).
  • Dynamic Action on LOV Items: Executes the validation function whenever a user changes selection.
  • Safety Dynamic Action on Controlling Field: Clears dependent LOVs if the controlling value changes to prevent invalid data.

Benefits:

  • Centralized and reusable logic
  • Real-time client-side validation
  • Maintains UI integrity
  • Minimal code duplication

Use Case Example

We have a Designation field (P22_DESIGNATION) and multiple multi-select LOVs. Rules:

Designation Maximum LOV Selections
Trainee 1
Consultant 2
Principle Consultant / Senior No restriction
Null / Not Selected Cannot select

Step 1: Global JavaScript Function

Place this in Global Page → Function and Global Variable Declaration:

function validateSelection(itemName) {
    var designation = $v('P22_DESIGNATION');
    var val = apex.item(itemName).getValue();
    apex.message.clearErrors();

    if (!designation) {
        apex.item(itemName).setValue('');
        apex.message.showErrors([{
            type: 'error',
            location: ['inline'],
            pageItem: itemName,
            message: 'Please select Designation first'
        }]);
        return;
    }

    if (!val) return;

    var values = Array.isArray(val) ? val : val.split(':');
    var maxAllowed;

    if (designation === 'Trainee') {
        maxAllowed = 1;
    } 
    else if (designation === 'Consultant') {
        maxAllowed = 2;
    } 
    else if (designation === 'Principle Consultant' || 
             designation === 'Principle Senior Consultant') {
        return; 
    }

    if (maxAllowed && values.length > maxAllowed) {
        var newValue = values.slice(0, maxAllowed).join(':');
        apex.item(itemName).setValue(newValue);

        apex.message.showErrors([{
            type: 'error',
            location: ['inline'],
            pageItem: itemName,
            message: 'Maximum ' + maxAllowed + 
                     ' selection(s) allowed for ' + designation
        }]);
    }
}

Step 2: Apply Dynamic Action on LOV Items

  • Event: Change
  • Action: Execute JavaScript Code
  • Code: validateSelection(this.triggeringElement.id);
  • Client-Side Condition: Item is NOT NULL

This ensures the validation runs automatically whenever a user selects values.

Step 3: Safety Mechanism on Designation Change

To prevent inconsistent data:

  • Create a Dynamic Action on P22_DESIGNATION
  • Event: Change
  • Action: Clear all dependent LOVs
Live Demo (Click Below)
View Demo: Dynamic LOV Selection in Oracle APEX

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