INF2603 - Databases 1, Chapter 1 - 5 Comprehensive Notes

Comprehensive vocabulary flashcards covering basic database concepts, data modeling styles, relational algebra, and advanced modeling techniques based on the Database 1 curriculum.

Data

Raw facts; facts not yet processed to reveal their meaning to the end user.

Information

The result of processing raw data to reveal its meaning (requires context) and facilitates decision making.

Metadata

Data about data through which end-user data is integrated and managed; describes data characteristics and relationships.

Database Management System (DBMS)

A collection of programs that manages the database structure and controls access to the data stored in the database.

Data Inconsistency

A condition occurring when different versions of the same data appear in different places.

Ad Hoc Query

A ‘spur-of-the-moment’ question or specific request for data manipulation issued in the form of $SQL$ code.

Workgroup Database

A multiuser database that usually supports fewer than $50$ users or is used for a specific department.

Data Warehouse

A specialized database containing historical data from operational databases, optimized for decision support.

Online Analytical Processing (OLAP)

A set of tools that provide advanced data analysis for retrieving, processing, and modeling data from a data warehouse.

Unstructured Data

Data that exists in its original (raw) state in the format in which it was collected.

Structural dependence

A data characteristic in which a change in the database schema affects data access, requiring changes in all access programs.

Data Redundancy

Exists when the same data is stored unnecessarily at different places; can result in poor security and data entry errors.

Data anomaly

A data abnormality in which inconsistent changes have been made to a database, such as update, insertion, or deletion anomalies.

Data Dictionary

A $DBMS$ component that stores metadata, including data definitions, characteristics, and relationships.

Entity

A person, place, thing, concept, or event for which data can be stored; represents a particular type of object in the real world.

Attribute

A characteristic of an entity or object, equivalent to fields in file systems.

Relationship

An association between entities, which can be One-to-many ($1:M$), Many-to-many ($M:N$), or One-to-one ($1:1$).

Constraint

A restriction placed on data, usually expressed in the form of rules, to ensure data integrity.

Business rule

A description of a policy, procedure, or principle within an organization used to define entities, attributes, and relationships.

Functional Dependence

A condition where an attribute $B$ is dependent on attribute $A$ ($A \rightarrow B$) if attribute $A$ determines exactly one value for $B$.

Primary Key (PK)

A candidate key selected to uniquely identify all other attribute values in any given row; it cannot contain null entries.

Foreign Key (FK)

An attribute in one table whose values must match the primary key in another table or be null, used to ensure referential integrity.

Candidate Key

A minimal superkey; a combination of attributes that can uniquely identify a record without any unnecessary data.

Referential Integrity

A condition in which a dependent table’s foreign key must have either a null entry or a matching entry in the related table's primary key.

Closure

A property of relational operators that permits the use of relational algebra operators on existing tables to produce new relations.

SELECT (RESTRICT)

A unary relational algebra operator ($\sigma$) that yields a horizontal subset of a table (horizontal partitioning).

PROJECT

A unary relational algebra operator ($\pi$) used to select a subset of columns or attributes (vertical partitioning).

Natural Join

A relational operation ($\Join$) that yields a new table composed of only rows with common values in their common attributes.

Composite Entity

An entity designed to transform an $M:N$ relationship into two $1:M$ relationships, also known as a bridge or associative entity.

Index

An ordered array of index key values and row $ID$ values (pointers) used to speed up and facilitate data retrieval.

Multivalued attribute

An attribute that can have many values for a single entity occurrence (e.g., multiple degrees for one employee).

Derived attribute

An attribute that does not physically exist within the entity but is calculated via an algorithm (e.g., age from birth date).

Existence-dependent

A property of an entity that can only exist if one or more other entities exist (indicated by a mandatory foreign key).

Recursive relationship

A relationship found within a single entity type, naturally occurring within a unary relationship.

Entity supertype

A generic entity type in a specialization hierarchy that contains the common characteristics of entity subtypes.

Subtype discriminator

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

Partial completeness

A condition in which some supertype occurrences might not be members of any subtype (represented by a single horizontal line).

Total completeness

A condition in which every supertype occurrence must be a member of at least one subtype (represented by a double horizontal line).

Surrogate key

A system-assigned primary key, generally numeric and auto-incremented, that has no intrinsic meaning in the user’s environment.

Time-variant data

Data whose values change over time and for which a history must be maintained (e.g., administrative appointments history).

Fan trap

A design trap occurring when one entity is in two $1:M$ relationships with other entities, resulting in an unexpressed association.