Doubt how to recover data from another table with Postgres

Question

I have two tables: Department with id and name

Telephone contains id_department and extension

I have already registered a department and some extensions where the id_departamento refers to the registered department

In Postgres, how would select for me to get all extensions related to the Department that I registered?

Answer 1

Select t.ramal from Telefone t 
    join Departamento d on d.id = t.id_departamento
where d.id = {id que vc quer} 

Obs: since id_department is a Foreign key I would change the name to fk_departamento