Systems Chapter 4

to transform the conceptual data model into a set of relations used for physical database design

• -Relational data structure: where data is stored
• -Data Manipulation: operations used to manipulate data in the data structure
• -Relational Data Integrity: rules that maintain integrity of the data when manipulated

the main data structure that stores and organized data in the relational data model

• - Column = attribute
• - Row = record/tuple

-Each relation is uniquely identified by its name

-Each cell of a relation contains exactly one (atomic) value

-Each record of a relation is unique

-Each attribute in a relation has a distinct name

-The values of an attribute are from the same domain

-The order of attributes is irrelevant

-The order of records is also irrelevant

key with more than one attribute

is a set of one or more attributes that uniquely identifies each record in a relation

is a minimal super key (minimum number of attributes)

a candidate key that has been selected to uniquely identify records in a relation

• -Must be unique within its domain at all times
• -The candidate key can never change
• -It cannot hold a NULL value

attribute or set of attributes in a relation that serves as a primary key of the same or some other relation

• -Domain Constraints: all values of an attribute must be from the same domain
• -Entity Constraints: ensure that every relation of a relational data model has a primary key and that it is not null
• -Referential Constraints: assures consistency between two relations that are linked through the primary key-foregin key relationship

set of values that can be assigned to an attribute

refers to a series of tests performed on relations to determine whether they satisfy or voilate the requirements of a normal form

• having duplicate data in the database
• -Increases storage use
• -Reduces efficiency of data updates

inconsistency problems caused by relations with redundant data

Abnormalities encountered while inserting new records into the relation

occur when data had been unintentionally removed from the relation

occur when there are multiple changes required to reflect a single attribute change

a relationship among attributes with a RELATION

Attributes on the left-hand side of the arrow in a functional dependency representation

-if all attributes appear in the functional dependency representation then the determinant is the super key

a pictorial representation of a functional dependency

functional dependency in which a non-primary key's attributes functionally depent of a part of (but not all) the primary key attributes

functional dependency in which a none of the attributes involves attributes of a primary key

each cell in the relation contains exactly one value

• -Already in first normal form
• -No partial functional dependencies

• -Already in second normal form
• -No transitive dependencies

• -Already in third normal form
• -Every deteminant is a candidate key