ISA 245 Exam 2

entity supertype

a generic entity type that contains the common characteristics of entity subtypes

entity subtype

a subset of an entity supertype; contains the unique characteristics of each entity

specialization hierarchy

A hierarchy based on the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype; based on grouping unique characteristics and relationships of the subtypes

inheritance

the ability of an object to inherit the data structure and methods of the classes above it in the class hierarchy

subtype discriminator

the attribute in the supertype entity that determines to which entity subtype each supertype occurrence is related

disjoint subtype

a unique and nonoverlapping subtype entity set

overlapping subtype

a condition in which each entity instance (row) of the supertype can appear in more than one subtype

completeness constraint

constraint that specifies whether each entity supertype occurrence must also be a member of at least one subtype; can be partial or total

entity cluster

a “virtual” entity type used to represent multiple entities and relationships in the ERD

3NF

when a table is in 2NF and no transitive dependencies

transitive dependency

a condition in which an attribute is dependent on another attribute that is not part of the primary key

BCNF(Boyce-Codd Normal Form)

a special type of third normal form (3NF) in which every determinant is a candidate key

4NF

when a table is in 3NF and contains no multiple independent sets of multivalued dependencies

multivalued dependency

an attribute that can have many values for a single entity occurrence.; For example, an EMP_ DEGREE attribute might store the string “BBA, MBA, PHD” to indicate three different degrees held

surrogate key

a system-assigned primary key, generally numeric and autoincremented

atomicity

the transaction property that requires all parts of a transaction to be treated as a single, indivisible, logical unit of work

granularity

the level of detail represented by the values stored in a table’s row; data stored at their lowest level of this are said to be atomic data

denormalization

a process by which a table is changed from a higher-level normal form to a lower-level normal form, usually to increase processing speed; this process potentially yields data anomalies

DDL(data definition language)

the language that allows a database administrator to define the database structure, schema, and subschema

create; alter

What are 2 DDL commands in SQL?

DML(data manipulation language)

set of commands that allows an end user to manipulate the data in the database

select; insert; update; delete; commit; rollback

What are 6 DML commands in SQL?

PK; FK; check condition; default; not null

5 classifications of constraints

commit

SQL command that permanently writes data changes to a database

rollback

SQL command that restores the database table contents to the condition that existed after the last COMMIT statement