代碼如下：

truncate之前

SQL> desc dual

Name? Type? ? ? ? Nullable Default Comments?

----- ----------- -------- ------- --------?

DUMMY VARCHAR2(1) Y? ? ? ? ? ? ? ? ? ? ? ? ?

SQL> select * from dual;

DUMMY

-----

X

SQL> truncate table dual;

Table truncated

SQL> select * from dual;

DUMMY

-----

不見了x，我好煩