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I would like to know whether there is any way, or how best, of restricting a relationship between two entities, one of which cannot be repeated in this relationship. I have the tables 'Customers' and 'Phone'. However 1 customer can have several phones, so I made a 'Customers' list. The problem is that you can’t repeat the phone number, but it has to exist on
tabela telefones.`create table cliente(
cod_cli int primary key,
nome varchar(40)
);
create table telefone(
identificador int primary key,
numero int unique
);
create table cliente_telefone(
id_cli_tel int primary key,
cod_cli int,
identificador int,
constraint fk_cli foreign key(cod_cli) references cliente(cod_cli),
constraint fk_tel foreign key(identificador) references telefone(identificador)
);
If the client can only have one phone, there is no need for the auxiliary table [cliente_phone], just add the column and Foreign key in the client table.
– Leandro Angelo
Hello @Wéllingthon M. de Souza. In my case I mentioned that the customer can have several phones, but in this table of relation, the phone id can repeat only once. It is as if the attribute 'identifier' (id_phone) was Foreign key and Unique at the same time in the cliente_phone table.
– João Paulo França