Constraints of E-R Modeling

An E-R enterprise schema may define certain constraints to which the contents of a database system must conform.

1. Mapping Cardinalities
   1. One to one
   2. One to many
   3. Many to one
   4. Many to many
2. Participation Constraints
   1. Total participation: If every entity in E participation is at least one relationship in R.
   2. Partial participation: If only some entities in E participate in relationships in R.