（164）Examine the command that is used to create a table:

SQL> CREATE TABLE orders(oid NUMBER(6) PRIMARY KEY, odate DATE, ccode NUMBER(6), oamt NUMBER(10,2)) TABLESPACE users;

Which two statements are true about the effect of the above command? (Choose two.)

A. A CHECK constraint is created on the OID column.

B. A NOT NULL constraint is created on the OID column.

C. The ORDERS table is the only object created in the USERS tablespace.  

D. The ORDERS table and a unique index are created in the USERS tablespace.

E. The ORDERS table is created in the USERS tablespace and a unique index is created on the OID column in the SYSTEM tablespace.

答案：（B、D）