OCP-1Z0-051-V9.02-32题

32. Which CREATE TABLE statement is valid?

A. CREATE TABLE ord_details        

(ord_no NUMBER(2) PRIMARY KEY, 

item_no NUMBER(3) PRIMARY KEY, 

ord_date DATE NOT NULL);

B. CREATE TABLE ord_details        

(ord_no NUMBER(2) UNIQUE, NOT NULL, 

item_no NUMBER(3), 

ord_date DATE DEFAULT SYSDATE NOT NULL);

C. CREATE TABLE ord_details        

(ord_no NUMBER(2) , 

item_no NUMBER(3), 

ord_date DATE DEFAULT NOT NULL, 

CONSTRAINT ord_uq UNIQUE (ord_no), 

CONSTRAINT ord_pk PRIMARY KEY (ord_no));

D. CREATE TABLE ord_details 

(ord_no NUMBER(2), 

item_no NUMBER(3), 

ord_date DATE DEFAULT SYSDATE NOT NULL, 

CONSTRAINT ord_pk PRIMARY KEY (ord_no, item_no));

Answer: D

答案解析

A，一个表只有一个主键。A错。

sys@TEST0910> CREATE TABLE ord_details

  2  (ord_no NUMBER(2) PRIMARY KEY,

  3  item_no NUMBER(3) PRIMARY KEY,

  4  ord_date DATE NOT NULL);

item_no NUMBER(3) PRIMARY KEY,

                  *

ERROR at line 3:

ORA-02260: table can have only one primary key

 

B答案：UNIQUE, NOT NULL之间不要逗号，列级约束不要逗号，B错

sys@TEST0910> CREATE TABLE ord_details        

  2  (ord_no NUMBER(2) UNIQUE, NOT NULL,

  3  item_no NUMBER(3), 

  4  ord_date DATE DEFAULT SYSDATE NOT NULL);

(ord_no NUMBER(2) UNIQUE, NOT NULL,

                          *

ERROR at line 2:

ORA-00904: : invalid identifier

 

逗号去掉可以创建，成功

sys@TEST0910> CREATE TABLE ord_details

  2  (ord_no NUMBER(2) UNIQUE NOT NULL,

  3  item_no NUMBER(3),

  4  ord_date DATE DEFAULT SYSDATE NOT NULL);

 

Table created.

 

C答案，两处错误，一个DEFAULT 后面没有指定默认值，一个是ord_no列的UNIQUE 和PRIMARY KEY

sys@TEST0910> CREATE TABLE ord_details        

  2  (ord_no NUMBER(2) ,

  3  item_no NUMBER(3), 

  4  ord_date DATE DEFAULT NOT NULL,

  5  CONSTRAINT ord_uq UNIQUE (ord_no), 

  6  CONSTRAINT ord_pk PRIMARY KEY (ord_no));

ord_date DATE DEFAULT NOT NULL,

                      *

ERROR at line 4:

ORA-00936: missing expression

 

 

sys@TEST0910> CREATE TABLE ord_details

  2  (ord_no NUMBER(2) ,

  3  tem_no NUMBER(3),

  4  ord_date DATE DEFAULT sysdate NOT NULL,

  5  CONSTRAINT ord_uq UNIQUE (ord_no),

  6   CONSTRAINT ord_pk PRIMARY KEY (ord_no));

CONSTRAINT ord_uq UNIQUE (ord_no),

                  *

ERROR at line 5:

ORA-02261: such unique or primary key already exists in the table

 

 

sys@TEST0910> CREATE TABLE ord_details

  2  (ord_no NUMBER(2) ,

  3  tem_no NUMBER(3),

  4   ord_date DATE DEFAULT sysdate NOT NULL,

  5  CONSTRAINT ord_pk PRIMARY KEY (ord_no));

 

Table created.

 

 

D答案，正确

sys@TEST0910>  CREATE TABLE ord_details

  2  (ord_no NUMBER(2), 

  3  item_no NUMBER(3), 

  4  ord_date DATE DEFAULT SYSDATE NOT NULL,

  5  CONSTRAINT ord_pk PRIMARY KEY (ord_no, item_no));

 

Table created.