OCP-1Z0-051-V9.02-21题

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.

Answer: BC

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12905109

准则

• 在使用子查询创建表时不复制LONG列。

• 不能在GROUP BY或ORDER BY子句中包括LONG列。

• 每个表只能使用一个LONG列。

• 不能对LONG列定义约束条件。

• 可以要求使用CLOB列，而不是LONG列。