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.

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