Database Systems Exam Notes

Data

A collection of raw facts and figures that can be processed to obtain meaningful information.

RDBMS

A database system where information is organized in tables consisting of rows and columns, supporting SQL commands and relationship mapping via keys.

Referential Integrity

A rule ensuring consistency across related tables by requiring foreign key values to correspond to an existing primary key.

Primary Key

An attribute or set of attributes that uniquely identifies each record in a table and cannot contain NULL values.

Second Normal Form (2NF)

A database schema condition requiring 1NF compliance and the complete absence of partial dependencies.

Relational Algebra Selection ($\sigma$)

An operation that filters and retrieves specific rows from a relation based on a specified condition.

Relational Algebra Projection ($\pi$)

An operation that isolates and retrieves specific columns from a relation.

Cartesian Product ($\times$)

A relational algebra operation that combines every row of one table with every row of another table.

Data Manipulation Language (DML)

The subset of SQL commands used to insert, update, and delete table records.

Database View

A virtual table formed by an SQL query that provides simplified access and security without storing redundant table data.