单项选择题
A.The DESCRIBE DEPT statement displays the structure of the DEPT table.
B.The ROLLBACK statement frees the storage space occupied by the DEPT table.
C.The DESCRIBE DEPT statement returns an error ORA-04043: object DEPT does not exist.
D.The DESCRIBE DEPT statement displays the structure of the DEPT table only if there is a COMMIT statement introduced before the ROLLBACK statement.
单项选择题 Click the Exhibit button and examine the data in the EMPLOYEES and DEPARTMENTS tables. You want to retrieve all employees, whether or not they have matching departments in the departments table. Which query would you use?（）
单项选择题 Which view should a user query to display the columns associated with the constraints on a table owned by the user?（）
单项选择题 Examine the description of the EMPLOYEES table: EMP_ID NUMBER(4) NOT NULL LAST_NAME VARCHAR2(30) NOT NULL FIRST_NAME VARCHAR2(30) DEPT_ID NUMBER(2) Which statement produces the number of different departments that have employees with last name Smith?（）