Left Join with multiple fields from the same table

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1

To build a lease, I have two tables.

The first is the contract, has some relationship fields as id_locador, id_locatario, id_fiador1, id_fiador2, among others. These fields are related to a table of people: id, nome, endereco, etc..

So all the people involved in the contract come from the same table "people".

How to make this relationship?

mysql sql delphi

2 answers

5

What you need is something like, for every relationship of contrato with your table pessoa, you add a left join

select C.ID_CONTRATO, PT.NOME AS TITULAR, PR.NOME AS RESPONSAVEL, PN.NOME AS NOTA
from 
    CONTRATO C 
        LEFT JOIN PESSOA PT ON C.ID_PESSOA = PT.ID_PESSOA
        LEFT JOIN PESSOA PR ON C.ID_PESSOA_RESPONSAVEL = PR.ID_PESSOA
        LEFT JOIN PESSOA PN ON C.ID_PESSOA_NOTA = PN.ID_PESSOA

-1

When you make a left Join it will automatically give the results of that junction having lines or not, because the left Join it works as a junction of the tables but meeting its condition as if it were an or, if you want to get back more concise data use Inner Join

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