CC104 CHAPTER 5

Relational Set Operators

1. SELECT 2. PROJECT 3. UNION 4. INTERSECT 5. DIFFERENCE 6. PRODUCT 7. JOIN 8. DIVIDE

Attribute domain

All values in a column have a specific range of values known as

Relational Database Model

Involves the use of data tables that collect groups of elements into relations. These models work based on the idea that each table setup will include a primary key or identifier

Schema

a logical grouping of database objects that are related to each other and serves as a blueprint on how the database is constructed.

Relation

are represented by tables

Key

consists of one or more attributes that determine other attributes.

Table

is a two-dimensional structure composed of columns and rows.

Table row

is called a tuple which represents a single instance of an entity within a set

Entity Integrity

is the condition in which each row in the table has its own unique identity

Foreign Key

is the primary of one table that has been placed into another table to create common attribute. used to ensure referential integrity. is used to prevent actions that would destroy links between tables. also prevents invalid data from being inserted into the foreign key column, because it has to be one of the values contained in the table it points to.

Referential Integrity

the condition in which every reference to an entity instance by another instance is valid

Primary Key

the key that uniquely identifies each row in a table. responsible for entity integrity requirements: value must be unique no key attribute in the primary key can contain null

Dependency

the value of one attribute makes it possible to determine the value of another