对于create我们知道这是一个ddl语句，另外还有一些操作，其实对于数据库来说也是ddl操作。当发生ddl操作时，有关对象的sql语句都会出现重新解析的情况，所以在生产环境下要注意此类操作。
1.在表上创建对象、在线重建索引
sql> create table dayu0718 as select * from dba_objects; Table created. sql> commit; Commit complete. sql> alter session set nls_date_format=‘yyyymmdd hh24:mi‘; Session altered. sql> select last_ddl_time from dba_objects where object_name=‘DAYU0718‘; LAST_DDL_TIME -------------- 20180718 13:37 sql> create index dayu0718_ind on dayu0718(object_id); Index created. sql> select last_ddl_time from dba_objects where object_name=‘DAYU0718‘; LAST_DDL_TIME -------------- 20180718 13:39 sql> alter index dayu0718_ind rebuild online; Index altered. sql> select last_ddl_time from dba_objects where object_name=‘DAYU0718‘; LAST_DDL_TIME -------------- 20180718 13:41
sql> alter table DAYU0718 add column_new varchar(30); Table altered. sql> select last_ddl_time from dba_objects where object_name=‘DAYU0718‘; LAST_DDL_TIME -------------- 20180718 13:50 sql> alter table DAYU0718 drop column column_new; Table altered. sql> select last_ddl_time from dba_objects where object_name=‘DAYU0718‘; LAST_DDL_TIME -------------- 20180718 13:51
3.
