How is Join and WHERE made with multiple tables?

Question

I have 4 tables they are already with Foreign key.

aluno:
id
matricula
username
curso_id          // referencia a id_cursos da tabela cursos, coluna id_cursos.

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cursos: 
id_cursos
nome_cursos

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modulos:
id_modulos
nome_modulos
cursos_id         //faz referencia a tabela cursos, coluna id_cursos.

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materias:
id_materias
nome_materias
modulos_id       // faz referencia a tabela modulos, coluna id_modulos.

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How do I Join to return the related columns of these tables ? if I run the code:

SELECT cursos.nome_curso, aluno.username 
FROM aluno JOIN cursos on cursos.id_cursos = aluno.curso_id;

will return only the relationship of these two tables, but the 4 are related as I would do this ?

Answer 1

Just add the other relationships in Join

SELECT C.nome_curso, A.username, M.nome_modulos, MA.nome_materias FROM aluno A
JOIN cursos C on C.id_cursos = A.curso_id
JOIN modulo M on M.id_modulos = C.id_cursos
JOIN materias MA on MA.id_materias = M.modulos_id

so if you have any relationship that doesn’t necessarily need to be filled, for example, materials, use LEFT JOIN

Answer 2

Just as I add the information of Thiago Loureiro, when selecting LEFT JOIN these choosing all the entries you have left and only those (right) that are found. The remaining (From the left) appear in the same but without the data from the right table.

If you do not, when no relation is found the left log is not shown, being "lost"

Answer 3

Just use the same logic as for a simple JOIN, only using LEFT OUTER JOIN

Select A.id, A.matricula, A.username, A.curso_id, B.id_cursos, B.nome_cursos, C.id_modulos, C.nome_modulos, C.cursos_id, D.id_materiais, D.nome_materiais, D.modulos_id 
FROM Aluno A LEFT OUTER JOIN Cursos B ON (A.curso_id = B.id_cursos),
LEFT OUTER JOIN Modulos C ON (B.id_cursos = C.cursos_id),
LEFT OUTER JOIN Materias D ON (C.id_modulos = D.modulos_id)