Chapter 3 - The Relational Database Model Flashcards
Attribute domain
Specific range of values for an attribute.
Candidate Key
A minimal (irreducible) superkey; a superkey that does not contain a subset of attributes that is itself a superkey.
Closure
Use of relational algebra operators on existing relations produces new relations.
Composite Entity
AKA Bridge or Associative entity. Helps avoid problems inherent to M:N relationships, includes the primary keys of tables to be linked
Composite key
Key that is composed of more than one attribute
Data Dictionary
Description of all tables in the database created by the user and designer. Metadata, data about the data.
Dependent
Attribute whose value is determined by the other attribute.
Determinant
Attribute whose value determines another.
Determination
State in which knowing the value of one attribute makes it possible to determine the value of another.
Domain
In data modeling, the construct used to organize and describe an attribute’s set of possible values.
Entity Integrity
Condition in which each row in the table has its own unique identity. All values in PK must be unique and no key attribute in the primary key can contain a null.
Equijoin
Links tables on the basis of an equality condition that compares specified columns of each table.
Flags
Special codes used to indicate the absence of some value.
Foreign Key (FK)
An attribute or combination of attributes in one table whose values must either match the primary key in another table or be null.
Full Functional Dependence
Entire collection of attributes in the determinant is necessary for the relationship.
Functional Dependence
Value of one or more attributes determines the value of one or more other attributes.
Homonym
Same name is used to label different attributes.
Index
Orderly arrangement to logically access rows in a table. Associated to only one table.
Index Key
Index’s reference point that leads to data location identified by the key.
Inner Join
Only returns matched records from the tables that are being joined.
Join Column(s)
Common columns in a natural join.
Key
An entity identifier based on the concept of functional dependence.
Key Attribute
Attribute that is a part of a key
Left Outer Join
Yields all of the rows in the first table, including those that do not have a matching value in the second table.
Linking Table
In the relational model, a table that implements an M:M relationship.
Natural Join
Links tables by selecting only the rows with common values in their common attributes.
Null
Absence of any data value that could represent:
Outer Join
Matched pairs are retained and unmatched values in the other table are left null.
Predicate Logic
Used extensively in mathematics to provide a framework in which an assertion (statement of fact) can be verified as either true or false.
Primary key (PK)
Attribute or combination of attributes that uniquely identifies any given row.
Referential Integrity
Every reference to an entity instance by another entity instance is valid.
Relational Algebra
Theoretical way of manipulating table contents using relational operators.
Relvar
Variable that holds a relation
Right Outer Join
Yields all of the rows in the second table, including those that do not have matching values in the first table.
Secondary Key
An attribute or combination of attributes used strictly for data retrieval purposes.
Set Theory
A part of mathematical science that deals with sets, or groups of things, and is used as the basis for data manipulation in the relational model.
Superkey
An attribute or combination of attributes that uniquely identifies each row in a table.
Synonym
Different names are used to describe the same attribute.
System Catalog
System data dictionary that describes all objects within the database.
Theta Join
Extension of natural join, denoted by adding a theta subscript after the JOIN symbol.
Tuple
A table row that represents a single entity occurrence within the entity set.
Union-Compatible
Tables share the same number of columns, and their corresponding columns share compatible domains.
Unique Index
Index key can have only one pointer value associated with it.
