Howard Paul

Sequential Access

Index Files and Data File Random Access

Relational Tables Random Access

A student has ID, last name, first name, address, , major field, … A course has ID, title, credits, prereq,… A student may take multiple courses in one term and grades are assigned. A student may take courses in multiple terms. A course may be offered in multiple terms. A term may have multiple courses offered.

A faculty has ID, last name, first name, address, , department, college, … A faculty may teach multiple courses in one semester. An offered course has ID, course number, year, term, faculty, classroom, and many students

Entity (Phy. Object, Relation, Table) Attribute (Property, Column) Relationship (Abs. Object, Relation) Record (Row)

The database has one or more tables A table has columns and rows Each cell may store at most one value Each table must have a Primary Key (PK) The PK represents a unique row of data A PK value and a column determines just a value A PK may consist one or more columns A table may contain PK columns of other tables, called Foreign Key (FK)