foreign keys constraints, depending on each other
От | zilch@home.se |
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Тема | foreign keys constraints, depending on each other |
Дата | |
Msg-id | 20010610213122.A29410@loony обсуждение исходный текст |
Ответы |
Re: foreign keys constraints, depending on each other
Re: foreign keys constraints, depending on each other Re: foreign keys constraints, depending on each other |
Список | pgsql-general |
I was just creating this little database for demonstrating the use of foreign keys constraints. I was about the create 3 tables, namely mother, father and child. Mother has a foreign key pointing at father ( id ), and father has a foreign key pointing at mother ( id ). Child has one pointer to mother ( id ) and one pointer to father ( id ). How can I prevent the error message from occurring? Ofcourse I see the problem here... just by taking away the references keyword from the mother table takes away the problem completely. --- DROP SEQUENCE mother_id_seq; DROP SEQUENCE father_id_seq; DROP SEQUENCE child_id_seq; DROP TABLE mother; DROP TABLE father; DROP TABLE child; CREATE TABLE mother ( id SERIAL, fatherID INT4 NOT NULL REFERENCES father ( id ) ON DELETE CASCADE, name TEXT, UNIQUE ( fatherID ) ); CREATE TABLE father ( id SERIAL, motherID INT4 NOT NULL REFERENCES mother ( id ) ON DELETE CASCADE, name TEXT, UNIQUE ( motherID ) ); CREATE TABLE child ( id SERIAL, motherID INT4 NOT NULL REFERENCES mother ( id ) ON DELETE CASCADE, fatherID INT4 NOT NULL REFERENCES father ( id ) ON DELETE CASCADE, name TEXT ); --- Thanks Daniel Akerud
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