Relational Model

• Components of Relational Model:

  1. Data Structure
  2. Data Manipulation
  3. Data Integrity
• Data Structure is composed of tables (relations), rows, and columns
• Data Manipulation is a powerful SQL operation for retrieving and modifying data
• Data Integrity is a mechanism for implementing business rules that maintain integrity of the manipulated data.
• Relation is a named, two dimensional table of data.
• True or False?

  All relations are in 1st Normal Form - True
• Requirements for a table to qualify as relation: (6)

  1. It must have a unique name
  2. Every attribute value must be atomic (not multivalued, not composite)
  3. Every row must be unique (Cannot have 2 or more rows with the same values)
  4. Attributes in tables must have unique names
  5. The order of columns are irrelevant
  6. The order of rows are irrelevant
• Relation corresponds with entity types and with many to many relationship
• Key Fields are special fields that serve two main purpose
• Primary Keys are unique identifiers of a relation. They guarantee that all rows are unique.
• Foreign Keys are identifiers that enable dependent relation to refer to its parent relation
• Integrity Constraints:

  1. Domain Constraints
  2. Entity Integrity
  3. Referential Integrity
• Domain constrains are the allowable values for the attributes
• Entity Integrity states that no primary key may be null
• Referential Integrity states that any foreign key value must match a primary key value in the relation of one side.