查看当前用户拥有的表

 select table_name from user_tables;

查看所有用户的表

 select table_name from all_tables;

查看当前用户下所有表注释

 select * from user_tab_comments;

查看当前用户下某表所有字段注释

 select * from user_col_comments where TABLE_NAME='某表名称';

日期:

片段1:

  to_char(t.opentime,'yyyymmdd') between '20190926' and '20191002'

片段2:

  t1.ADDTIME BETWEEN TO_DATE('2019-10-16 00:00:00', 'yyyy-mm-dd hh24:mi:ss') 

片段3:

  AND TO_DATE('2019-10-16 23:59:59', 'yyyy-mm-dd hh24:mi:ss')

片段4:

  TO_CHAR(addtime, 'YYYY-MM-DD') BETWEEN '2019-09-01' AND '2019-09-30'

清除与新建:

  drop table cgs_wx_user__info_temp1 purge;

  create table cgs_wx_user__info_temp1 nologging as (select。。。。。。。。)

改变表增加字段及更新

  alter table cgs_wx_use_info_temp add(zhywgls number);

  update cgs_wx_use_info_temp a set zhywgls = (select zhywgls from  cgs_wx_user__info_temp1 b  where b.CITYNAME = 'blank')  where a.DcitynameD = 'blank' ; 

  commit;