External ID

External ID in Salesforce is a custom field that has the “External ID” attribute checked meaning that it contains unique record identifiers from a system outside of Salesforce. When we select this option the import wizard will detect existing records in Salesforce that have the same External Identification.

This operation is case-insensitive but if the custom field has a separate “Unique” attribute then the case sensitive option for that field is selected which means Uppercase and Lowercase letters will not be considered identical.

An object can have at most 7 External IDs’ fields. The field type should be any one of auto-number, email, number, or text. Custom fields marked as unique also count against an object’s limit of 7 External IDs’ fields.

Let’s move forward to Record ID.