（单选题）Which statement adds a co

题目描述

AALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

BALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;

CALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn NOT NULL;

DALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn IS NOT NULL;

EALTER TABLE customers MODIFY name CONSTRAINT cust_name_nn NOT NULL;

FALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name NOT NULL;