Backend Developer
mediumsql-joins-explained
Explain SQL joins (INNER, LEFT, RIGHT) with practical use cases.
Answer
Joins combine rows from multiple tables.
- **INNER JOIN:** only matching rows
- **LEFT JOIN:** all left rows + matching right rows (NULL when missing)
- **RIGHT JOIN:** opposite of LEFT (less common)
**Use cases:**
- INNER for required relationships (orders with customers)
- LEFT for optional relationships (users with optional profiles)
**Interview tip:** mention join keys should be indexed and types should match.
Related Topics
SQLDatabases