单项选择题
A. The two statements produce identical results.
B. The second statement returns a syntax error.
C. There is no need to specify DESC because the results are sorted in descending order by default.
D. The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement.
单项选择题 Examine the data in the EMPLOYEES table. EMPLOYEES EMP_NAME DEPT_ID MGR_ID JOB_ID SALARY EMPLOYEE_ID 101 Smith 20 120 SA_REP 4000 102 Martin 10 105 CLERK 2500 103 Chris 20 120 IT_ADMIN 4200 104 John 30 108 HR_CLERK 2500 105 Diana 30 108 IT_ADMIN 5000 106 Smith 40 110 AD.ASST 3000 108 Jennifer 30 110 HR_DIR 6500 110 Bob 40 EK_DIR 8000 120 Revi 20 110 SA_DIR 6500 On the EMPLOYEES table, EMPLOYEE_ID is the primary key. MGR_ID is the ID of managers and refers to the EMPLOYEE_ID. The JOB_ID column is a NOT NULL column. Evaluate this DELETE statement: DELETE employee_id, salary, job_id FROM employees WHERE dept_id = 90; Why does the DELETE statement fail when you execute it?（）
单项选择题 The EMP table has these columns: ENAME VARCHAR2(35) SALARY NUMBER(8,2) HIRE_DATE DATE Management wants a list of names of employees who have been with the company for more than five years. Which SQL statement displays the required results?（）
单项选择题 What is necessary for your query on an existing view to execute successfully?（）