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单项选择题Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?（）

A、ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

B、ALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

C、ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn NOT NULL;

D、ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn IS NOT NULL;

E、ALTER TABLE customers MODIFY name CONSTRAINT cust_name_nn NOT NULL;

F、ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name NOT NULL;

  • C

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