单项选择题
A. ALTER TABLE students ADD PRIMARY KEY _ id;
B. ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student_id);
C. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY student_id;
D. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY (student_id);
E. ALTER TABLE students MODIFY CONSTRAINT stud_id_pk PRIMARY KEY (student_id);
单项选择题 You are the DBA for an academic database. You need to create a role that allows a group of users to modify existing rows in the STUDENT_GRADES table. Which set of statements accomplishes this? （）
单项选择题 Evaluate this SQL statement: SELECT ename, sal, 12* sal+100 FROM emp; The SAL column stores the monthly salary of the employee. Which change must be made to the above syntax to calculate the annual compensation as "monthly salary plus a monthly bonus of $100, multiplied by 12"? （）
单项选择题 Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?（）