What types of JOINs do you know in SQL?

In SQL, the following main types of JOINs are used to combine rows from two or more tables:

• INNER JOIN — returns only those rows where there are matches in both tables based on the join condition.

• LEFT JOIN (LEFT OUTER JOIN) — returns all rows from the left table and matching rows from the right. If there are no matches, the columns from the right table will be NULL.

• RIGHT JOIN (RIGHT OUTER JOIN) — similar to LEFT JOIN, but returns all rows from the right table and matching rows from the left.

• FULL JOIN (FULL OUTER JOIN) — returns all rows from both tables, matching and non-matching, with NULLs where there is no match.

• CROSS JOIN — Cartesian product of two tables, each row of the first table is joined with every row of the second.

• SELF JOIN — when a table is joined with itself, usually using aliases.

Example of INNER JOIN:

SELECT employees.name, departments.name
FROM employees
INNER JOIN departments ON employees.department_id = departments.id;