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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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?（）

Column definitions cannot be altered to add DEFAULT values.

A change to the DEFAULT value affects only subsequent insertions to the table.

Column definitions cannot be altered at add DEFAULT values for columns with a NUMBER data type.

All the rows that have a NULL value for the SALARY column will be updated with the value 5000.

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考题 The EMPLOYEE tables has these columns:LAST_NAME VARCHAR2(35)SALARY NUMBER(8,2)COMMISSION_PCT NUMBER(5,2)You want to display the name and annual salary multiplied by the commission_pct for all employees. For records that have a NULL commission_pct, a zero must be displayed against the calculated column.Which SQL statement displays the desired results? （）A. SELECT last_name, (salary * 12) * commission_pct FROM EMPLOYEES;B. SELECT last_name, (salary * 12) * IFNULL(commission_pct, 0) FROM EMPLOYEES;C. SELECT last_name, (salary * 12) * NVL2(commission_pct, 0) FROM EMPLOYEES;D. SELECT last_name, (salary * 12) * NVL(commission_pct, 0) FROM EMPLOYEES;

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