As you can see, there can be several Entity-relationship diagram notations that are used to represent the structure and model of a database. Though, there are different Crow’s Foot notations that can help you depict the uniqueness and relationship between different entities (known as Cardinality). In the Crow’s Foot notion, three major symbols can be used in different ways to depict cardinality: 1. A ring that represents a zero 2. A dash that represents one. 3. Crow’s Foot that represents many.