单项选择题
A. SELECT * FROM emp_dept_vu;
B. SELECT department_id, SUM(salary) FROM emp_dept_vu GROUP BY department _ id;
C. SELECT department_id, job_id, AVG(salary) FROM emp_dept_vu GROUP BY department _ id, job_id;
D. SELECT job_id, SUM(salary) FROM emp_dept_vu WHERE department_id IN (10,20) GROUP BY job_id HAVING SUM (salary) > 20000
E. None of the statements produce an error; all are valid.
多项选择题 Which four statements correctly describe functions that are available in SQL?（）
单项选择题 Examine the structure of the EMPLOYEES and NEW_EMPLOYEES tables: EMPLOYEES EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2 (25) LAST_NAME VARCHAR2 (25) HIRE_DATE DATE NEW EMPLOYEES EMPLOYEE_ID NUMBER Primary Key NAME VARCHAR2 (60) Which DELETE statement is valid?（）
单项选择题 Examine the structure of the STUDENTS table: You need to create a report of the 10 students who achieved the highest ranking in the course INT SQL and who completed the course in the year 1999.Which SQL statement accomplishes this task?（）