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Oracle Certificate Profession 1Z0-051-27

原创 Oracle 作者:LuiseDalian 时间:2014-05-10 06:56:59 0 删除 编辑
(27)Which two statements are true regarding tables?

A. A table name can be of any length.

B. A table can have any number of columns.

C. A column that has a DEFAULT value cannot store null values.

D. A table and a view can have the same name in the same schema.

E. A table and a synonym can have the same name in the same schema.

F. The same table name can be used in different schemas in the same database.

答案:(F)

解析:

--C(X) 具有默认值的列是可以插入null值的

CREATE TABLE t

(

  col1 NUMBER(2),

  col2 VARCHAR2(10) DEFAULT 'hello'

);

insert into t values(1, null);

scott@TESTDB11>select * from t;

      COL1 COL2

---------- ----------

         1

        

--E(X),同一方案中不允许任何两个对象具有相同的名称

scott@TESTDB11>create synonym emp for hr.employees;

create synonym emp for hr.employees

               *

ERROR at line 1:

ORA-00955: name is already used by an existing object

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