Salesforce Platform Developer Practice Exam

Which field type cannot be set as an external ID?

1. Date

2. Number

3. eMail

4. Text

The correct answer is: Date

The field type that cannot be set as an external ID is the Date field. External IDs in Salesforce are used to uniquely identify records from an external system, and they need to have certain characteristics to function properly. Date fields, while they are used to store important data, do not provide a unique identification capability that fits the requirement to match records from external systems. On the other hand, Number fields, Email fields, and Text fields can all serve as external IDs because they can hold values that uniquely identify a record. Numbers can represent unique identifiers such as account numbers, email addresses can uniquely identify users, and text fields can hold unique usernames or codes. Therefore, the inability to use the Date field as an external ID stems from its nature; dates do not have the uniqueness required for linking external records effectively.