5、 choose two:

You executed the following CREATE TABLE statement that resulted in an error:

SQL> CREATE TABLE employees(

emp_id NUMBER(10) PRIMARY KEY,

ename VARCHAR2(20),

email NUMBER(3) UNIQUE,

address VARCHAR2(500),

phone VARCHAR2 (20),

resume LONG,

hire_date DATE,

remarks LONG,

dept_id NUMBER(3) CONSTRAINT emp_dept_id_fk REFERENCES departments(dept_id) ,

CONSTRAINT ename_nn NOT NULL(ename));

Identify two reasons for the error.

 

A) The PRIMARY KEY constraint in the EMP_ID column must have a name and must be defined at the

table level only.

B) The FOREIGN KEY keyword is missing in the constraint definition.

C) Only one LONG column can be used per table.

D) FOREIGN KEY defined on the DEPT_ID column must be at the table level only.

E) The NOT NULL constraint on the ENAME column must be defined at the column level.

 

Answer:CE

一个表中最多只能用一个LONG类型：

NOT NULL约束是放在定义的字段后面：

NOT NULL约束放在定义的字段后就可以了：