Entity-Relationship Diagram Presentation Gianna-lee Williams 6AQ Ms. Anderson

What is an Entity-Relationship Diagram An Entity-Relationship Diagram is a tool used for process modeling that graphically shows the connections among entities in a system.

What are the symbols used in ERD and explain each. 1. Entities : these are usually nouns used in descriptions of the system, in the discussion of business rules, or in documentation. 2. Relationships : these are usually verbs used in descriptions of the system or in discussion of the business rules (entity ______ entity). 3. Attributes to the relations; these are determined by the queries, and may also suggest new entities or they may suggest the need for keys or identifiers.

What is a one-to-one relationship with example. In a one-to-one relationship each item of entity A can be associated with 0 or 1 item of entity B.

What is a one-to-many relationship with example. When one data item can be linked to 0, 1 or many other data items, you are dealing with a one-to-many relationship.

What is a many-to-many relationship with example. The many-to-many relationship is a relationship where multiple rows from table A can correspond to multiple rows in table B. An example of such a relationship is a school where teachers teach students.