单项选择题 Which SQL statement would you use to remove a view called EMP_DEPT_VU from your schema?（）

多项选择题 Which four are valid Oracle constraint types? （）

单项选择题 The EMPLOYEES table contains these columns: EMPLOYEE_ID NUMBER(4) ENAME VARCHAR2 (25) JOB_ID VARCHAR2(10) Which SQL statement will return the ENAME, length of the ENAME, and the numeric position of the letter "a" in the ENAME column, for those employees whose ENAME ends with a the letter "n"?（）