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