Relational Algebra and Calculus Flashcards

Flashcards covering key vocabulary from the Relational Algebra and Calculus lecture.

Relational Algebra

Basic set of operations for the relational model.

Relational Algebra Expression

Sequence of relational algebra operations.

Relational Calculus

Higher-level declarative language for specifying relational queries.

SELECT Operation

Subset of the tuples from a relation that satisfies a selection condition.

PROJECT Operation

Selects columns from a table and discards the other columns.

Degree

Number of attributes in attribute list.

UNION (R ∪ S)

Includes all tuples that are either in R or in S or in both R and S. Duplicate tuples eliminated.

INTERSECTION (R ∩ S)

Includes all tuples that are in both R and S.

SET DIFFERENCE (or MINUS) (R – S)

Includes all tuples that are in R but not in S.

JOIN Operation

Combine related tuples from two relations into single 'longer' tuples.

THETA JOIN

Each of the form Ai θ Bj, where θ (theta) is one of the comparison operators: {=,

EQUIJOIN

In case the operator θ is the equality operator (=) then this join is also called an equijoin.

Inner Join

Type of match and combine operation, defined formally as a combination of CARTESIAN PRODUCT and SELECTION

Recursive Closure Operation

Operation applied to a recursive relationship between tuples of same type

Outer Join

Keep all tuples in R, or all those in S, or all those in both relations regardless of whether or not they have matching tuples in the other relation

Declarative Expression

Specify a retrieval request using a nonprocedural language.

Tuple Variables

Ranges over a particular database relation.

Truth Value

Truth value of an atom evaluates to either TRUE or FALSE for a specific combination of tuples

Domain Relational Calculus

Variables range over single values from domains of attributes

Aggregate Functions

Functions that summarize data from multiple rows into a single output value.

Grouping Operation

Groups tuples based on the values of specified attributes.

HAVING Clause

Specifies a condition for groups, typically used with aggregate functions.

Query Tree

Represents the execution plan of a query as a tree structure.

Query Optimization

Process of selecting the most efficient execution plan for a query.

Cost-Based Optimization

Uses statistical information and cost models to estimate the cost of different execution plans.

Heuristic Optimization

Applies rules and heuristics to improve the execution plan.

Materialization

Process of storing the intermediate results of a query on disk.

Pipelining

Passes the results of one operation directly to the next without materialization.

Hashing

Technique used to improve the performance of join operations.

Relational Model

Represents data as a set of relations or tables.

Attribute

A column in a relation that represents a characteristic of an entity.

Tuple

A row in a relation representing a single entity or record.

Relation Schema

The structure of a relation including the name and attributes.

Relation Instance

A set of tuples in a relation at a particular point in time.

Database Schema

The overall design of the database, including all relation schemas.

Database Instance

The data in the database at a particular point in time.

Key

An attribute or set of attributes that uniquely identifies a tuple in a relation.

Primary Key

A key chosen to be the main identifier of a relation.

Foreign Key

An attribute in one relation that refers to the primary key of another relation.

Referential Integrity

Ensures that relationships between relations remain consistent.

NULL Value

Represents an unknown or missing value in an attribute.

Superkey

A set of attributes that uniquely identifies a tuple in a relation.

Candidate Key

A minimal superkey, meaning no proper subset is a superkey.

Functional Dependency

A constraint between two sets of attributes in a relation.

Normalization

Organizing data to reduce redundancy and improve data integrity.

First Normal Form (1NF)

Eliminate repeating groups of data.

Second Normal Form (2NF)

Be in 1NF and eliminate redundant data.

Third Normal Form (3NF)

Be in 2NF and eliminate transitive dependencies.

Boyce-Codd Normal Form (BCNF)

A stricter form of 3NF.

Denormalization

Adding redundancy to improve performance.

Data Integrity

Ensuring data is accurate, consistent, and reliable.

Atomicity

A transaction property that ensures all or nothing is written.

Consistency

Ensures a transaction maintains database constraints.

Isolation

Ensures concurrent transactions do not interfere with each other.

Durability

Ensures that once a transaction is committed, it remains so.

ACID Properties

Atomicity, Consistency, Isolation, Durability.