（31）Evaluate the following SQL commands:

The command to create a table fails. Identify the reason for the SQL statement failure? (Choose all that apply.)

A. You cannot use SYSDATE in the condition of a CHECK constraint.

B. You cannot use the BETWEEN clause in the condition of a CHECK constraint.

C. You cannot use the NEXTVAL sequence value as a DEFAULT value for a column.

D. You cannot use ORD_NO and ITEM_NO columns as a composite primary key because ORD_NO is also the FOREIGN KEY.

答案：（A、C）

解析：

--C

create sequence seq_t

start with 1

increment by 1

maxvalue 10

nocycle

nocache;

create table t

(

col1 number(2),

col2 number(4) default seq_t.nextval

)

col2 number(4) default seq_t.nextval

*

ERROR at line 4:

ORA-00984: column not allowed here

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OCP 1Z0-051-31