Context

Joins are one of the most important SQL concepts because real datasets are usually split across multiple tables. Interviewers often ask this to check whether you understand both result shape and business meaning.

Core question

Explain the main types of joins in SQL and how they differ. Your answer should cover:

1. What each join returns
2. How unmatched rows are handled
3. When each join is appropriate
4. A simple SQL example for each join type

Scope guidance

Keep the explanation practical and interview-focused. You should be able to describe INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, CROSS JOIN, and SELF JOIN, and mention common mistakes such as filtering a LEFT JOIN in a way that turns it into an INNER JOIN.