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單項選擇題
Click the Exhibit button and examine the data in the EMPLOYEES table.
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.
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