Difference between connecting tables with WHERE and with INNER JOIN

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I was learning SQL and came across the following instructions:

SELECT 
    tbl_Livros.Nome_Livro, tbl_Livros.ISBN_Livro, tbl_Autores.Nome_Autor
FROM 
    tbl_Livros, tbl_Autores
WHERE 
    tbl_Livros.AutorID_Livro = tbl_Autores.ID_Autor;

And the other:

SELECT 
    tbl_Livros.Nome_Livro, tbl_Livros.ISBN_Livro, tbl_Autores.Nome_Autor
FROM 
    tbl_Livros
INNER JOIN tbl_Autores ON tbl_Livros.AutorID_Livro = tbl_Autores.ID_Autor;

The 2 commands returned me the same records, I wonder what difference between them. The difference between INNER JOIN and OUTER JOIN I know, but the difference between INNER JOIN and link using WHERE I don’t know.

Thank you.

sql

  • Where is to filter the query and innerjoin serves to connect keys in 2 or more tables. Oinnerjoin tras para vc a query in two tables being linked by a key Primary or a key Foreign

  • 1

    If the query optimizer is doing the right job, there should be no difference between these queries. They are only two ways to specify the same desired result.

1 answer

1

Here’s a visual example of my comet:

Assuming we have two tables with a ratio of 1 to 1 inserir a descrição da imagem aqui

Note the filter behavior of WHERE in the two consultations and in the 2nd Consultation observe the INNER JOIN

inserir a descrição da imagem aqui

Summarizing the INNER JOIN - Returns row when there is at least one match in both tables.

  • Resumindo o INNER JOIN - Retorna linha quando houver pelo menos uma correspondência em ambas as tabelas. and the where also. As I said: If the query optimizer is doing the right job, there should be no difference between these queries. They are only two ways to specify the same desired result.

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