The Relational Data Model Flashcards
Relational Data Model
A data model representing data in the form of tables.
Relation
A two dimensional table containing rows and columns of data.
Recursive Relationship
A relationship that relates an object set to it self.
Relation Attribute
A column in a relation
Degree of a relation
The number of attributes in a relation
Tuple
A row in a relation
Attribute Domain
The set from which an attribute takes its values.
Null Value
The value given an attribute in a tuple if the attribute is applicable or its value is unknown.
Super Key
A set of attributes that uniquely identifies each row in a relation.
Key
A minimal set of attributes that uniquely identifies each row in a relation.
Functionally Determine
To uniquely determine a value.
Composite Key
A key consisting of more than one attribute.
Candidate Key
Any set of attributes that could be chosen as a key of a relation.
Primary Key
The candidate key designated for principal use in uniquely identifying rows in a relation.
Foreign Key
A set of attributes in one relation that constitutes a key in some other or possibly the same relation used to indicate logical links between relations.
Recursive Foreign Key
A foreign key that references its own relation.
Relational Database Schema
A listing showing relation names attributes and foreign keys
Constraint
A rule that restricts the values in a database.
Entity Integrity Rule
The value of a non-null foreign key must be an actual key value in some relation.
Normalization
The process of converting a relation to a standard form.
Data Redundancy
Repetition of data in database.
Data Integrity
Consistency of data in a database.
Update Anomaly
Data inconsistency resulting from data redundancy and partial update,
Deletion Anomaly
Unintended loss of data due to deletion of other data.
Insertion Anomaly
In ability to add data to the database due to the absence of other data.
Decomposition of Relations
Splitting a relation into multiple relations.
Normal Forms
Rules for structuring relations that eliminate anomalies.
First Normal Form(1NF)
All attribute values use must be atomic.
Atomic Values
Value that is not a set of values or a repeating group.
Functional Dependent
The value of an attribute in a tuple determines the value of another attribute in the tuple.
Determinant
The attributes on the left side of a functional dependency determine the value of other attributes in the tuple.
Second Normal Form(2NF)
No non-key attribute may be function ally dependent on just a part of the key.
Projection of A Relation
A relation consisting of selected attributes from another relation.
Third Normal Form(3NF)
Every determinant is a key.
Boyce-Codd normal form(BCNF)
Every determinant is a key.
Transitive Dependency
Occurs when a non-key attribute is functionally dependent on one or more other non-key attributes.
Multivalued Dependency (MVD)
A constraint that guarantees the mutual independence of multivalued attributes.
Fourth Normal Form(4NF)
A relation that is in third normal form and has no multivalued dependencies.
Fifth Normal Form(5NF)
A normal form that eliminates join dependencies.
Domain/Key normal form (DKNF)
Requires every constraints to result from definitions of domains and keys.
