Question

São dadas a seguir duas tabelas no banco de dados PostgreSQL: orders e customers. CREATE TABLE customers ( customer_id SERIAL PRIMARY KEY, customer_name VARCHAR(100) ); CREATE TABLE orders ( order_id SERIAL PRIMARY KEY, order_date DATE, customer_id INT, FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ); Qual alternativa altera a definição dessa chave estrangeira de modo que, quando um registro na tabela customers for deletado, a coluna customer_id na tabela orders seja atualizada para NULL?

Accepted Answer

D) ALTER TABLE orders DROP CONSTRAINT orders_customer_id_fkey, ADD CONSTRAINT orders_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE SET NULL;

Answer

A) ALTER TABLE orders DROP CONSTRAINT orders_customer_id_fkey, ADD CONSTRAINT orders_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE RESTRICT NULL;

Answer

B) ALTER TABLE orders DROP CONSTRAINT orders_customer_id_fkey, ADD CONSTRAINT orders_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE CASCADE NULL;

Answer

C) ALTER TABLE orders DROP CONSTRAINT orders_customer_id_fkey, ADD CONSTRAINT orders_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES customers(customer_id) ON DELETE SET DEFAULT NULL;

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