Databases Beginner

What is JOIN?

An SQL operation that combines rows from two or more tables based on a related column between them.

JOINs are fundamental to querying relational databases. INNER JOIN returns rows with matches in both tables. LEFT JOIN returns all rows from the left table plus matches from the right. RIGHT JOIN is the reverse. FULL OUTER JOIN returns all rows from both tables.

CROSS JOIN produces the Cartesian product. Self-joins join a table with itself. Proper indexing on join columns is critical for performance.

Learn More About This Topic

SQL for Absolute Beginners

Closely related

SQLite Fundamentals

Closely related

Redis Fundamentals

Related reading

Related Terms

A virtual table defined by a SQL query that provides a simplified or restricted view of data from one or more tables.

Time-Series Database

A database optimized for storing and querying timestamped data points like metrics, sensor readings, and event logs.

A database object that automatically executes a specified function when certain events (INSERT, UPDATE, DELETE) occur on a table.

A data structure that improves the speed of data retrieval operations on database tables at the cost of additional storage.

A middleware server that sits between applications and databases, providing connection pooling, load balancing, and query routing.

ORM (Object-Relational Mapping)

A technique that lets you interact with a database using object-oriented code instead of writing raw SQL queries.

View All Databases Terms →