单项选择题 Examine the description of the MARKS table: STD_ID NUMBER(4) STUDENT_NAME VARCHAR2(30) SUBJ1 NUMBER(3) SUBJ2 NUMBER(3) SUBJ1 and SUBJ2 indicate the marks obtained by a student in two subjects. Examine this SELECT statement based on the MARKS table: SELECT subj1+subj2 total_marks, std_id FROM marks WHERE subj1 > AVG(subj1) AND subj2 > AVG(subj2) ORDER BY total_ marks; What is the result of the SELECT statement?（）

单项选择题 Evaluate the SQL statement: SELECT ROUND(TRUNC(MOD(1600,10),-1),2) FROM dual; What will be displayed?（）

单项选择题 The EMP table contains these columns: LAST NAME VARCHAR2(25) SALARY NUMBER(6,2) DEPARTMENT_ID NUMBER(6) You need to display the employees who have not been assigned to any department. You write the SELECT statement: SELECT LAST_NAME, SALARY, DEPARTMENT_ID FROM EMP WHERE DEPARMENT_ID = NULL; What is true about this SQL statement?（）