PostgreSQL JOINS: Make a join with three tables to find the name, jobs, department name and ID of all the employees working in London

3. Write a SQL query to make a join with three tables employees, departments and locations to find the name, including first_name and last_name, jobs, department name and ID, of the employees working in London.

Sample Solution:

Code:

SELECT e.first_name, e.last_name, e.job_id, e.department_id, d.department_name 
FROM employees e 
JOIN departments d 
ON (e.department_id = d.department_id) 
JOIN locations l ON 
(d.location_id = l.location_id) 
WHERE l.city = 'London';

Sample table: employees

Sample table: locations

Sample table: departments

Output:

pg_exercises-# FROM employees e
pg_exercises-# JOIN departments d
pg_exercises-# ON (e.department_id = d.department_id)
pg_exercises-# JOIN locations l ON
pg_exercises-# (d.location_id = l.location_id)
pg_exercises-# WHERE l.city = 'London';
 first_name | last_name | job_id | department_id | department_name
------------+-----------+--------+---------------+-----------------
 Susan      | Mavris    | HR_REP |            40 | Human Resources
(1 row)

Relational Algebra Expression:

Relational Algebra Tree:

Practice Online

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Previous: Write a query to make a join with employees and departments table to find the name of the employee, including first_name and last name, department ID and name of departments.
Next: Write a query to make a join with two tables employees and itself to find the employee id, last_name as Employee along with their manager_id and last name as Manager.