20.choose two

Examine the description of the EMP_DETAILS table given below:

Which two statements are true regarding SQL statements that can be executed on the EMP_DETAIL table?

A) You cannot add a new column to the table with LONG as the data type.

B) An EMP_IMAGE column can be included in the GROUP BY clause.

C) You can alter the table to include the NOT Nun., constraint on the EMP_IMAGE column.

D) An EMP_IMAGE column cannot be included in the ORDER BY clause.

Answer:AD

(解析：

答案 A：

SQL> alter table sales add emp_info long;

alter table sales add emp_info long *

第 1 行出现错误:

ORA-01754: 表只能包含一个 LONG 类型的列。

答案 D：

SQL> select * from sales

2 order by emp_image;

select * from sales

*

第 1 行出现错误:

ORA-00997: 非法使用 LONG 数据类型

）