多项选择题
A.The UNIQUE constraint does not permit a null value for the column.
B.A UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.
C.The PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.
D.The NOT NULL constraint ensures that null values are not permitted for the column.
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?（）
单项选择题 What does the FORCE option for creating a view do?（）