oracle - 为什么截断表不会更改上次 DDL 日期？

Question

当我运行以下代码时，我注意到Last DDL Date 没有更改。

 execute immediate 'truncate table my_table';

问题是什么？

提前致谢

Answer 1

truncate 表仅在表不为空时截断表。

如果表为空，那么当您执行truncate table 命令时，它不会被截断。

在此处查看演示:

SQL> select OBJECT_NAME, LAST_DDL_TIME from user_objects where OBJECT_NAME = 'CONTR';

OBJECT_NAME  LAST_DDL_TIME
------------ --------------------
CONTR        13-nov-2019 11:45:53

SQL> truncate table CONTR; -- empty table

Table truncated.

SQL> select OBJECT_NAME, LAST_DDL_TIME from user_objects where OBJECT_NAME = 'CONTR';

OBJECT_NAME  LAST_DDL_TIME
------------ --------------------
CONTR        13-nov-2019 11:45:53

SQL> INSERT INTO CONTR VALUES (1,1,1,1); -- filling values in the table

1 row created.

SQL> commit;

Commit complete.

SQL> truncate table CONTR;

Table truncated.

SQL> select OBJECT_NAME, LAST_DDL_TIME from user_objects where OBJECT_NAME = 'CONTR';

OBJECT_NAME  LAST_DDL_TIME
------------ --------------------
CONTR        13-nov-2019 11:47:46

SQL> -- time is changed now

干杯!!