Joins in SQL are essential to query data from multiple tables in relational databases effectively.

Inner Join

Returns matching rows between tables.

Left Join

Returns all rows from left table and matching rows from right.

Right Join

Returns all rows from right table and matching rows from left.

Full Outer Join

Returns all rows when there is a match in either table.

Example

SELECT employees.name, departments.dept_name
FROM employees
LEFT JOIN departments ON employees.dept_id = departments.id;

Understanding joins is critical for complex query building.