Chapter 5 - Data Modeling Using the (Enhanced) Entity-Relationship (E-ER) Model provides about Example Database Application (COMPANY), ER Model Concepts, ER Diagrams - Notation, ER Diagram for COMPANY Schema, Enhanced Entity Diagram. | CSC271 Database Systems Lecture # 5 Summary: Previous Lecture Database languages Functions of a DBMS DBMS environment Data models and their categories The Relational Model Chapter 3 History of Relational Model Proposed by . Codd in 1970 “ A relational model of data for large shared data banks” Objectives of relational model High degree of data independence Dealing with issues . data semantics, consistencies, and redundancy To enable the expansion of set-oriented data manipulation languages Examples of RDBMSs Oracle Microsoft SQLServer Microsoft Access Visual FoxPro InterBase JDataStore R:Base Relational Model Based on mathematical concept of a relation Which is physically represented as a table Codd, a trained mathematician, used terminology taken from mathematics, principally set theory and predicate logic Relational Model Terminology A relation is a table with columns and rows Only applies to logical structure of the database (external and conceptual level of ANSI-SPARC architecture), not the physical structure Attribute is a named column of a relation Domain is the set of allowable values for one or more attributes Relational Model Terminology Tuple is a row of a relation Degree is the number of attributes in a relation Cardinality is the number of tuples in a relation Relational Database is a collection of normalized relations with distinct relation names Instances of Sample Relations Examples of Attribute Domains Alternative Terminology Mathematical Relations Consider two sets, D1 & D2, Where D1 = {2, 4} and D2 = {1, 3, 5} Cartesian product, D1 x D2 is, Set of all ordered pairs, where first element is member of D1 and second element is member of D2 D1 x D2 = {(2, 1), (2, 3), (2, 5), (4, 1), (4, 3), (4, 5)} Alternative way is to find all combinations of elements with first from D1 and second from D2 Mathematical Relations Any subset of Cartesian product is a relation; . R = {(2, 1), (4, 1)} May specify which pairs are in relation using some . | CSC271 Database Systems Lecture # 5 Summary: Previous Lecture Database languages Functions of a DBMS DBMS environment Data models and their categories The Relational Model Chapter 3 History of Relational Model Proposed by . Codd in 1970 “ A relational model of data for large shared data banks” Objectives of relational model High degree of data independence Dealing with issues . data semantics, consistencies, and redundancy To enable the expansion of set-oriented data manipulation languages Examples of RDBMSs Oracle Microsoft SQLServer Microsoft Access Visual FoxPro InterBase JDataStore R:Base Relational Model Based on mathematical concept of a relation Which is physically represented as a table Codd, a trained mathematician, used terminology taken from mathematics, principally set theory and predicate logic Relational Model Terminology A relation is a table with columns and rows Only applies to logical structure of the database (external and conceptual level of ANSI-SPARC .
