问题：
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?（）
A . There is no row with dept_id 90 in the EMPLOYEES table.
B . You cannot delete the JOB_ID column because it is a NOT NULL column.
C . You cannot specify column names in the DELETE clause of the DELETE statement.
D . You cannot delete the EMPLOYEE_ID column because it is the primary key of the table.
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?（）
● 参考解析
本题暂无解析
