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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 DEPARTMENT_ID = NULL; What is true about this SQL statement ?（）
A:The SQL statement displays the desired results.
B:The column in the WHERE clause should be changed to display the desired results.
C:The operator in the WHERE clause should be changed to display the desired results.
D:The WHERE clause should be changed to use an outer join to display the desired results.

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出自：Oracle认证

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