Database Reference
In-Depth Information
Formal Terminology
Conceptual Physical
relation table
attribute field
tuple record
3.5.1 Constraint and Cardinality
Constraints are some rules to store or retrieve data from a database. They restrict users what
data can be stored and retrieved. Constraints should be added after a logical data model is
stable. A primary key consists of one or more attributes of an entity that distinguishes each
record from the others. Cardinality (or degree) concerns the number of instances involved
in a relationship. A relationship can be said to be either a 1:1 (oneto-one) relationship, a
1:M (one-to-many) relationship, or a M:M (many-to-many) relationship.
3.6 ENTITY RELATIONSHIP MODELING
