What approaches can be used instead of the JOIN operator to combine tables in SQL?

Instead of the JOIN operator in SQL, the following approaches can be used to combine data from multiple tables:

1. Subqueries – nested queries that return data for filtering or selection.

SELECT * FROM employees WHERE department_id IN (SELECT id FROM departments WHERE name = 'Sales');

2. Using UNION or UNION ALL operators – combine the results of two or more queries with the same structure.

SELECT name FROM table1
UNION
SELECT name FROM table2;

3. Cross Product (CROSS JOIN) – returns the Cartesian product, but is usually used with filtering.

4. Processing at the application level – retrieve data from different tables separately and combine them in code (for example, in Python).

However, the JOIN operator is the most efficient and readable way to combine tables in most cases.