A matching rule defines how duplicate records are identified. We have predefined standard matching rules, but we can create new matching rules by going to Setup | Duplicate Management | Matching Rules and clicking on New Rule. Select the External Contact object.
Let's create a rule with the following configuration:
Matching rule creation
The Matching Criteria section states which conditions should trigger the potential duplicate match. Matching methods define the algorithm used to compare values and can be set to Exact to be triggered only if we have the same value or Fuzzy: type to provide specific data type algorithms ...
