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 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.