Database Dr. Roueida Mohammed

The Relational Data Model  Specific relational data model concepts like attributes, tuples, domains, relations, domains, schemas, keys  The relational data model constraints like entity integrity, referential integrity, and semantic constraints which are used to enforce rules on a relational database  Relational algebra operations like union, intersection, difference, Cartesian product, selection, projection, join and division which are used to manipulate relations in a relational data model  Relational calculus which is an alternative to the relational algebra as a candidate for the manipulative part of the model

Basic concepts Attributes Domains Tuples Relations Schemas Keys

The types of keys: Candidate keys Primary keys . Foreign keys

Relational data model constraints . Entity integrity constraint Referential integrity constraint Semantic integrity constraints

Transforming an E/R Design into a Relational Design  Turn each entity set into a relation with the same set of attributes.  Replace a relationship by a relation whose attributes are the keys for the connected entity sets.

Relational algebra Relational algebra is a set of operators to manipulate relations. Each operator of the relational algebra takes either one or two relations as its input and produces a new relation as its output.

We defined 8 such operators, two groups of 4 each:  The traditional set operations: union, intersection, difference and Cartesian product  The special relational operations: select, project, join and divide.