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
题目
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); Which 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 to 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.