SQL JOINs combine rows from two or more tables using related columns.
An INNER JOIN returns records that exist in both tables. A LEFT JOIN returns all records from the left table and matching records from the right table. A RIGHT JOIN performs the opposite operation.
For example, a job portal may contain a users table and an applications table. Joining these tables allows the application to retrieve a candidate's details together with their job applications.
JOIN questions are extremely common in SQL interviews, so developers should practise writing queries rather than only memorizing definitions.