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--ÈçºÎÓÃgrade±íµÄ×ÊÁÏÈ¥¸üÐÂusertable±íµÄ×ÊÁÏ£¨ÓйØÁªµÄ×Ö¶Îuserid£©
 update usertable u set u.grade =
 (select g.grade from grade g where g.userid = u.userid);
 
--ÈçºÎʹ²éѯ½á¹û×Ö¶ÎÉú³ÉÐòºÅ
select rownum, t.* from sm_t_pad_new t
--ÈçºÎ¿ìËÙ×öÒ»¸öºÍÔ­±íÒ»ÑùµÄ±¸·Ý±í
 create table new_table as (select * from user);
--ÈçºÎ²é¿´Êý¾ÝÎļþµÄ´æ·Å·¾¶
select tablespace_name, file_id, bytes/1024/1024, file_name
from dba_data_files order by file_id;
--²éѯÐÕÃûÏàͬµÄÔ±¹¤µÄÐÅÏ¢
select u1.userid, u1.username from user u1,
(select username, count(*) from user group by username having count(username) > 1) u2
where u1.username = u2.username;
--¸ù¾Ýʱ¼ä²éѯ
select * from user
where create_time >= to_date('2010-4-16 00:00:00','YYYY-MM-DD HH24:mi:ss')
and create_time <= to_date('2010-4-16 12:00:00','YYYY-MM-DD HH24:mi:ss')