Dependent Field

The pattern: confirm both Controlling and Dependent fields exist as picklists, create the dependency, map the matrix with Include All as starting point, pair with Validation Rule for API-level enforcement. The setup is straightforward; the discipline is in the validation rule pairing.

1. 1
   Create the Controlling and Dependent picklists first

   Both fields must exist before the dependency can be created. Build the picklists with their full value sets.

2. 2
   Open Field Dependencies for the object

   Object Manager, pick the object, Fields and Relationships, Field Dependencies. Click New.

3. 3
   Pick Controlling and Dependent fields

   Controlling is the field whose value drives the dependency. Dependent is the field whose available values change based on Controlling.

4. 4
   Use Include All to start the matrix

   Enable every combination as the starting point. Then disable invalid cells. Faster than enabling cells one at a time for large picklists.

5. 5
   Save and test in the UI

   Open a record, pick a Controlling value, confirm the Dependent picklist refreshes correctly. Test multiple Controlling values.

6. 6
   Add a Validation Rule for API enforcement

   Field Dependencies enforce only in the UI. A Validation Rule that asserts the same constraint at the platform level holds the dependency across Data Loader and API.

7. 7
   Document the dependency rationale

   The matrix is not self-explanatory. Document the intent in object documentation so future admins understand why specific combinations are disabled.