Atomicity:
Atomicity means a transaction follows the “all or nothing” rule. If one part of a transaction fails, the whole transaction fails.
Attribute:
An attribute is a named column of a relation (table).
Business Logic:
The sequence of steps or rules that control how a business process works.
Candidate Key:
A candidate key is a set of attributes that uniquely identifies a record in a table. One of them is selected as the primary key.
Cardinality:
Cardinality is the number of tuples (rows) in a relation.
Conceptual Level:
The community view of the database that describes what data is stored and the relationships between data.
Consistency:
Consistency ensures that only valid data is written to the database. If a transaction breaks rules, it is rolled back.
Cursor:
A cursor is a database object used to move through query results one record at a time.
Data:
Data is a collection of raw facts and figures.
Data Manipulation Language (DML):
A language used to insert, update, delete, and retrieve data from a database.
Data Definition Language (DDL):
A language used to define and describe database structure such as tables and relationships.
Data Dictionary:
A central repository of information about data including meaning, relationships, format, and usage.
Data Independence:
Data independence means changes in lower levels do not affect higher levels of the database.
Data Model:
A collection of concepts used to describe data, relationships, and constraints.
Data Warehouse:
A central repository where data from multiple databases is stored for analysis.
Database:
A shared collection of logically related data designed to meet the information needs of an organization.
Database Schema:
The overall structure and description of a database.
DBMS (Database Management System):
Software that allows users to create, manage, and control access to databases.
Degree:
Degree of a relation is the number of attributes (columns) in a table.
Domain:
A domain is the set of allowed values for an attribute.
Durability:
Durability ensures that once a transaction is committed, it will not be lost even after system failure.
Enterprise:
An organization that uses computer systems and applications, usually on a large scale.
Enterprise Constraints:
Additional rules defined by users or database administrators in a database.
Entity:
An entity is a real-world object about which data is stored, such as Student or Employee.
Entity Integrity:
Entity integrity means the primary key cannot contain NULL values.
Entity-Relationship Diagram (ERD):
A graphical diagram used to show entities and their relationships in a database.
External View:
The user’s view of the database, showing only the data relevant to that user.
File-based System:
A system where each application program manages its own data files.
Foreign Key:
An attribute in one table that refers to the primary key of another table.
Functional Dependency:
A relationship where one attribute determines another attribute, written as A → B.
Internal View:
The physical storage view of the database that shows how data is stored in the system.
Logical Data Independence:
Ability to change the conceptual schema without affecting external schemas.
Metadata:
Metadata is data about data, describing structure and meaning.
Non-Procedural DML:
A language where the user specifies what data is required, not how to get it.
Null:
Null represents a missing, unknown, or not applicable value.
ODBC (Open Database Connectivity):
A standard that allows different database systems to communicate with each other.
Physical Data Independence:
Ability to change internal schema without affecting conceptual schema.
Primary Key:
The candidate key chosen to uniquely identify each row in a table.
Procedural DML:
A language where the user specifies how to retrieve or manipulate data step by step.
Query:
A request used to retrieve or analyze data from a database.
Referential Integrity:
Ensures that a foreign key must match a primary key in another table or be NULL.
Relation:
A relation is a table consisting of rows and columns.
Relational Database:
A database made up of multiple related tables (relations).
Relational Schema:
The structure of a relation including its attributes and domains.
Super Key:
A set of attributes that uniquely identifies a row in a table.
System Catalog:
A system table that stores metadata about the database structure.
Tuple:
A tuple is a row in a relation (table).