How to do Inner Join in mysql?

Question

I have 2 tables in my database, Categories and Cars. The table categories has a PK Id_category and Name. Already Automobiles has a PK Id_automoveis and the other columns that make up this table INCLUDING the FK Id_categoria as you can see in the image below:

I’m starting my studies in databases with mysql but I’m having a lot of difficulties in relational models and Inner Join. If there’s something wrong I can change it too!

This database is handled by a PHP system.

Answer 1

Your database is not normalized. First, it would normalize the BD, thus creating the tables:

• Brand;
• Model;
• Coloured;
• Category;
• Automobile;

After that, I would think about doing the queries, where you can use different joins:

INNER JOIN or JOIN only: Returns records that have values corresponding in both tables;

LEFT JOIN: returns all the records from the table on the left and the corresponding records from the right table;

RIGHT JOIN: return all records from the right table and the Corresponding records from the left table;

FULL (OUTER) JOIN: Returns all records when there is one match in left or right table

Answer 2

Try it buddy:

select
    *
from
    categorias c
inner join
    automoveis a
on a.ID_Categoria = c.ID_categoria