SF-Admin Object Manager and Lightning App Builder Practice Question
Universal Containers has a custom object 'Equipment__c' with a field 'Serial_Number__c' that must be unique across all records. The administrator needs to enforce this uniqueness. What should the administrator do?
⚠ Common exam trap
The trap here is assuming that validation rules can check for duplicates by querying other records, but they cannot; only the unique field setting provides a hard constraint.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Mark the Serial_Number__c field as unique in the field definition.
To enforce uniqueness for a custom field, the administrator should mark the field as unique in its definition. This creates a database constraint that prevents duplicate values. Validation rules cannot query other records, duplicate rules are not strict, and formula fields do not enforce uniqueness.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Mark the Serial_Number__c field as unique in the field definition.
Why this is correct
Salesforce allows administrators to mark a custom field as unique, which enforces that no two records can have the same value. This is done in the field definition under 'Unique'. It is the simplest and most direct way to enforce uniqueness for a custom field on a custom object.
- ✗
Use a formula field to concatenate Serial_Number__c with the record ID.
Why it's wrong here
A formula field cannot enforce uniqueness. Concatenating with the record ID would make each value unique but would not prevent duplicate Serial_Number__c values from being entered. The formula would simply create a new unique string, but the original field could still have duplicates. This does not meet the requirement.
- ✗
Create a duplicate rule and matching rule for Equipment__c.
Why it's wrong here
Duplicate rules and matching rules identify possible duplicates and can alert or block users, but they do not strictly enforce uniqueness at the database level. They are used for data quality management and can be bypassed. They are not the correct tool for a hard uniqueness constraint.
- ✗
Create a validation rule on Equipment__c that checks if the Serial_Number__c value already exists.
Why it's wrong here
Validation rules cannot query other records; they can only evaluate the current record's fields and related parent fields. They cannot check for duplicates across records. Therefore, a validation rule cannot enforce uniqueness of Serial_Number__c. A different feature is required.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Salesforce exam blueprint
This SF-Admin practice question is part of Courseiva's free Salesforce certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SF-Admin exam.