5.2: Mapping an E-R Diagram to a Relation
A model of a database (that is, the design) is based on but not uniquely determined by the model of the requirements (the conceptual design). In other words, a given conceptual design can be transformed to one of several designs depending on the design decisions made. This transition from requirements to design is called mapping. This subunit discusses mapping from an E-R model to a relational model.
For software development, it is generally desirable to use methods and models for each phase that are compatible, which eases the transition from one phase to another. So too with databases. This video maps an E-R model to a relational model that supports the requirements analysis and design of a database, and covers the transition between the two.
Read chapter 9, which presents constraints on attributes or tables. A constraint is a rule for incorporating semantics of the application data into the relational model. There are constraints for database integrity, application semantics, business rules,