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.
加在 OID 列上的是主键约束，包含唯一约束和非空约束，A 错，B 对
因为 OID 上有主键索引，所以会自动创建唯一索引，也在 USERS 表空间，CE 错，D 对