Inner - Equijoin

The old style join method.

    SELECT *
    FROM employees,departments
    WHERE employees.department_id = department.department_id

and the common attribute will be shown

Equijoin = Calculate from Cartesian Product → Match the rows that have a match on WHERE statement → Merge the table → Remove the foreign key

To merge the table, the common key need to be typed in, else the sql may not able to merge them (because they can have multiple common attribute

    SELECT *
    FROM employee e, departments d, locations l
    WHERE e.department_id = d,.department_id
    AND d.location_id = l.location_id

# Inner - Equijoin