OCP-1Z0-051-V9.02-36题

36. Examine the following SQL commands: 

SQL>CREATE TABLE products (

prod_id NUMBER(3) CONSTRAINT p_ck CHECK (prod_id > 0),

prod_name CHAR(30),

prod_qty NUMBER(6),

CONSTRAINT p_name NOT NULL, 

CONSTRAINT prod_pk PRIMARY KEY (prod_id));

SQL>CREATE TABLE warehouse (

warehouse_id NUMBER(4),

roomno NUMBER(10) CONSTRAINT r_id CHECK(roomno BETWEEN 101 AND 200),

location VARCHAR2(25),

prod_id NUMBER(3),

CONSTRAINT wr_pr_pk PRIMARY KEY (warehouse_id,prod_id),

CONSTRAINT prod_fk FOREIGN KEY (prod_id) REFERENCES products(prod_id));

Which statement is true regarding the execution of the above SQL commands?

A. Both commands execute successfully.

B. The first CREATE TABLE command generates an error because the NULL constraint is not valid.

C. The second CREATE TABLE command generates an error because the CHECK constraint is not valid.

D. The first CREATE TABLE command generates an error because CHECK and PRIMARY KEY

constraints cannot be used for the same column.

E. The first CREATE TABLE command generates an error because the column PROD_ID cannot be used

in the PRIMARY KEY and FOREIGN KEY constraints. 

Answer: B

答案解析：

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

第一个命令报错，因为CONSTRAINT p_name NOT NULL不能定义为表级，第一个命令里的CHECK和主键约束能用在相同的列上。

 

sh@TESTDB> create table pro

  2  (prod_id number,

  3  prod_name char(30),

  4  constraint p_name not null);

constraint p_name not null)

                  *

ERROR at line 4:

ORA-00904: : invalid identifier

A错误，因为第一个报错。

B正确，NOT NULL不能定义为表级，只能定义为列级

C错误，between可以用在check约束里

D错误，check和主键约束可以用在同一列

E错误，可以把主键作为其他表的外键