单项选择题
A.ALTER TABLE students ADD PRIMARY KEY student_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);
多项选择题 Click the Exhibit button and examine the data from the EMP table. The COMMISSION column shows the monthly commission earned by the employee. Which three tasks would require subqueries or joins in order to be performed in a single step?（）
单项选择题 Evaluate this SQL statement: SELECT e.EMPLOYEE_ID,e.LAST_NAME,e.DEPARTMENT_ID, d.DEPARTMENT_NAME FROM EMPLOYEES e, DEPARTMENTS d WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID; In the statement, which capabilities of a SELECT statement are performed?（）
单项选择题 Click the Exhibit button and examine the data from the ORDERS and CUSTOMERS tables. Evaluate this SQL statement: SELECT cust_id, ord_total FROM orders WHERE ord_total > ANY(SELECT ord_total FROM orders WHERE cust_id IN (SELECT cust_id FROM customers WHERE city LIKENew York)); What is the result when the above query is executed?（）