有个题目请大家帮忙看下

[guye1986]

21. Examine the description of the EMP_DETAILS table given below:
name NULL TYPE
EMP_ID NOT NULL NUMBER
EMP_NAME NOT NULL VARCHAR2 (40)
EMP_IMAGE LONG
Which two statements are true regarding SQL statements that can be executed on the EMP_DETAIL
table? (Choose two.)
A. An EMP_IMAGE column can be included in the GROUP BY clause.
B. An EMP_IMAGE column cannot be included in the ORDER BY clause.
C. You cannot add a new column to the table with LONG as the data type.
D. You can alter the table to include the NOT NULL constraint on the EMP_IMAGE column.

为什么C是对的，C不是就是不能在一个表中加一个long字段的新列吗？
我试了貌似可以呢？？？

[linwaterbin]

引用 楼主 guye1986 的回复:

21. Examine the description of the EMP_DETAILS table given below: name NULL TYPE EMP_ID NOT NULL NUMBER EMP_NAME NOT NULL VARCHAR2 (40) EMP_IMAGE LONG Which two statements are true r……

hr@ORCL> create table emp_details (emp_id number not null,emp_name varchar2(40) not null,emp_image long);

Table created.

hr@ORCL> alter table emp_details add (test_c long);
alter table emp_details add (test_c long)
                             *
ERROR at line 1:
ORA-01754: a table may contain only one column of type LONG

[guye1986]

引用 1 楼 linwaterbin 的回复:

引用 楼主 guye1986 的回复:21. Examine the description of the EMP_DETAILS table given below: name NULL TYPE EMP_ID NOT NULL NUMBER EMP_NAME NOT NULL VARCHAR2 (40) EMP_IMAGE LONG Which two st……

恩 我错了 额。。谢谢！！

[hetic]

一个表中只能有1个Long 类型列，我问下楼主 D 选项应该是对的吧， 可以在Long类型列上 添加非空constraint ，为什么答案没有选择D