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【单选题】
The EMPLOYEES table has these columns: LAST NAME VARCHAR2(35) SALARY NUMBER(8,2) HIRE_DATE DATE Management wants to add a default value to the SALARY column. You plan to alter the table by using this SQL statement: ALTER TABLE EMPLOYEES MODIFY ( SALARY DEFAULT 5000); What is true about your ALTER statement?（）
A.
Column definitions cannot be altered to add DEFAULT values.
B.
A change to the DEFAULT value affects only subsequent insertions to the table.
C.
Column definitions cannot be altered at add DEFAULT values for columns with a NUMBER data type.
D.
All the rows that have a NULL value for the SALARY column will be updated with the value 5000.
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A.
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B.
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C.
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D.
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