Appendix B: Glossary of SQL Terms
In this appendix, you’ll find a glossary of common SQL terms and their definitions, helping you understand and navigate the world of SQL databases.
A
ACID
- Definition: ACID stands for Atomicity, Consistency, Isolation, and Durability, which are the four properties that guarantee the reliability of database transactions.
C
Column
- Definition: A column, also known as a field or attribute, is a vertical entity in a database table that contains all the information associated with a specific data type.
Constraint
- Definition: A constraint is a rule or condition enforced on a database to maintain data integrity, such as uniqueness, primary key, foreign key, and check constraints.
D
Database
- Definition: A database is an organized collection of structured data stored and managed in a computer system, typically managed by a database management system (DBMS).
DDL (Data Definition Language)
- Definition: DDL is a subset of SQL used to define, modify, and remove the structure of database objects such as tables, indexes, and views.
DML (Data Manipulation Language)
- Definition: DML is a subset of SQL used to retrieve, insert, update, and delete data from a database, typically through SELECT, INSERT, UPDATE, and DELETE statements.
I
Index
- Definition: An index is a data structure used to improve the speed of data retrieval operations on a database table by providing quick access to rows based on the values of specific columns.
J
Join
- Definition: A join is an SQL operation used to combine rows from two or more tables based on a related column between them, allowing users to retrieve related data from multiple tables in a single query.
K
Key
- Definition: A key is a column or set of columns in a database table used to uniquely identify each row, such as a primary key, unique key, or foreign key.
Q
Query
- Definition: A query is an SQL statement used to retrieve data from a database based on specified criteria, such as SELECT, INSERT, UPDATE, and DELETE statements.
R
Relational Database
- Definition: A relational database is a type of database management system (DBMS) that organizes data into tables with rows and columns, and establishes relationships between tables using keys.
S
Schema
- Definition: A schema is a collection of database objects, including tables, views, indexes, and constraints, that defines the structure and organization of a database.
T
Transaction
- Definition: A transaction is a sequence of one or more SQL statements executed as a single unit of work, ensuring the consistency and integrity of database operations.
V
View
- Definition: A view is a virtual table generated by an SQL query that presents data from one or more tables in a predefined format, allowing users to retrieve and manipulate data without modifying the underlying tables.