多项选择题
A.DELETE employees;
B.DESCRIBE employees;
C.ROLLBACK TO SAVEPOINT C;
D.GRANT SELECT ON employees TO SCOTT;
E.ALTER TABLE employees SET UNUSED COLUMN sal;
F.SELECT MAX(sal) FROM employees WHERE department_id = 20;
多项选择题 Which two statements are true about constraints? （）
单项选择题 What is true about joining tables through an equijoin?（）
单项选择题 Click the Exhibit button to examine the structure of the EMPLOYEES, DEPARTMENTS, and LOCATIONS tables. Two new departments are added to your company as shown: DEPARTMENT_ID DEPARTMENT_NAME MGR_ID LOCATION_ID 9998 Engineering 123 9999 Administrative Boston You need to list the names of employees, the department IDs, the department names, and the cities where the departments are, even if there are no employees in the departments and even if the departments are not yet assigned to a location. You need to join the EMPLOYEES, DEPARTMENTS, and LOCATIONS tables to retrieve this information. Which statement do you execute to retrieve this information?（）