Examine the command that is used to create a table： SQL> CREATE TABLE orders（oid NUMBER（6） PRIMARY KEY， odate DATE， ccode NUMBER （6）， oamtNUMBER（10，2）） TABLESPACE users； Which two statements are true about the effect of the above command（）

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 columnin the SYSTEM tablespace.