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） （）
- AA CHECK constraint is created on the OID column.
- BA NOT NULL constraint is created on the OID column.
- CThe ORDERS table is the only object created in the USERS tablespace.
- DThe ORDERS table and a unique index are created in the USERS tablespace.
- EThe ORDERS table is created in the USERS tablespace and a unique index is created on the OIDcolumn in the SYSTEM tablespace.