Common Oracle commands

1)oracle Backup data a user
（ Not in sqlplus, It is executed in the operating system ,cmd etc. , need dba jurisdiction ）
expdp tempuser/oracle DUMPFILE=suncrs20170105.DMP DIRECTORY=EXPDP_DIR1 SCHEMAS=suncrs logfile=suncrs20170105.dmp.log REUSE_DUMPFILES=Y
Be careful not to add the real example name , The real example name is wrong ： And linux Need to be in oracle Execute under the installation user

2) Restore table data
Flashback （ Flashback query requires rollback segment support , Can query the front image of data . But when the rollback segment size is not enough , The old data will be covered , So what can flashback is a time range , It is impossible to do it at any time ）
a) If you enable flashback, you can use the flashback table .
select log_mode,flashback_on from v$database;
If it is the following result, it will flash back
LOG_MODE FLASHBACK_ON

alter table Table name enable row movement; -- Enable table row movement
flashback table Table name to timestamp to_timestamp(‘20130813 14:00:00’,‘yyyymmdd hh24:mi:ss’);

b) Flashback query ：
select *
from test_tmp as of timestamp to_timestamp(‘2014-05-28 11:00:00’,‘yyyy-mm-dd hh24:mi:ss’); Back to 2014 year 05 month 28 Japan 11 spot

c) Delete data table by mistake , Use the recycle bin to recover
SELECT * FROM user_recyclebin WHERE original_name=‘drop_test’;
FLASHBACK TABLE drop_test TO BEFORE DROP;
– Rename the table when recovering from the recycle bin ( Keep watch A Rename the recovery table B
flashback table surface A to before drop rename to surface B;)
purge table Table name ;– Delete the table specified in the recycle bin
purge recyclebin;– Empty your Recycle Bin . Pay attention to the operation , Don't empty it easily
drop table Table name purge;– Delete your table and no longer leave any traces in the recycle bin

3) Delete duplicate data ： utilize rowid Realization
eg: delete FROM hdm.dtmg_data_exrt a
WHERE ROWID NOT IN (SELECT MAX(b.rowid)
FROM hdm.dtmg_data_exrt b
WHERE a.crcycd = b.crcycd
AND a.torycd = b.torycd
AND a.etl_dt = b.etl_dt);

4) One query record changes to multiple display , utilize rownum Realization （ Repeat display ）
SELECT t.* FROM ca_bat_task t, (SELECT rownum FROM ca_bat_task where rownum between 1 and 2) t2
where t.shortname=‘BDSS’ ORDER BY TASK_CODE ASC;

5) View locked session( need sys jurisdiction ）
View locked session,
SELECT OBJECT_NAME,MACHINE,S.SID,S.SERIAL# FROM V$LOCKE{D}_{O}BJECTL,DB{A}_{O}BJECTSO,V$SESSION S WHERE L.OBJECT_ID=O.OBJECT_ID AND L.SESSION_ID=S.SID;
Kill session;
ALTER SYSTEM KILL SESSION ‘100,17235’;
ALTER SYSTEM disconnect SESSION ‘1264,32387’ immediate;

6) See the failed index , And rebuild (DROP PARTITION The post index will be invalid ）
SELECT INDEX_NAME,STATUS FROM USER_INDEXES WHERE STATUS=‘UNUSABLE’;
ALTER INDEX INDEX_NAME REBUILD;