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?（）AColumn definitions cannot be altered to add DEFAULT values.BA change to the DEFAULT value affects only subsequent insertions to the table.CColumn definitions cannot be altered at add DEFAULT values for columns with a NUMBER data type.DAll the rows that have a NULL value for the SALARY column will be updated with the value 5000.
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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