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How do I create a query on two tables?

To create a relationship between two tables in SQL we can use the traditional method, or the JOIN statement.

Imagine the following tables, composed of the respective fields:

  • authors
    • aut_id
    • aut_nome
  • books
    • lib_id
    • lib_autore
    • lib_titolo
The field lib_autore, numerical, will have the same value as the id of the author of the homonymous table.

We see the classic method to write the SQL code: 





 SELECT * FROM authors, books







 WHERE







 aut_id = lib_autore
We see the method that provides education JOIN: 





 SELECT * FROM authors







 INNER JOIN books







 ON = aut_id lib_autore

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