Flashback Version Query、Flashback Transaction Query快速闪回细粒度数据

Flashback Version Query 闪回版本查询

使用Flashback Version Query  返回在指定时间间隔或SCN间隔内的所有版本，一次commit命令就会创建一个版本。

语法如下：

SELECT .....FROM tablename VERSIONS {BETWEEN {SCN | TIMESTAMP} start AND end}

--start,end可以是时间也可以是scn

Flashback Version Query伪列说明

versions_start{scn|time}  版本开始的scn或时间戳

versions_end{scn|time}  版本结束scn或时间戳，如果有值表明此行后面被更改过是旧版本，如果为null，则说明行版本是当前版本或行被删除（即versions_operation值为D）。

versions_xid 创建行版本的事务ID

versions_operation  在行上执行的操作（I=插入，D=删除，U=更新）

示例说明：

SQL> create table xyc_t1 as select * from emp where 1=2;  --创建表xyc_t1

Table created.

SQL> select to_date(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual; --查询时间作为timestamp开始时间

TO_DATE(SYSDATE,'YY
-------------------
2013-10-06 08:17:58

SQL> insert into xyc_t1 select * from emp where empno=7902;   --插入empno=7902

1 row created.

SQL> commit;                                                                               --插入一行提交作为一个版本

Commit complete.

SQL> insert into xyc_t1 select * from emp where empno=7788;

1 row created.

SQL> insert into xyc_t1 select * from emp where empno=7698;

1 row created.

SQL> commit;                                                                             --插入两行提交作为一个版本

Commit complete.

SQL> update xyc_t1 set sal=8888 where empno=7788;

1 row updated.

SQL> commit;                                                                          --再次更改empno=7788的行提交，使这行有旧版本

Commit complete.

SQL> select to_date(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual; --查询时间作为timestamp结束时间

TO_DATE(SYSDATE,'YY
-------------------
2013-10-06 08:20:01

/*

select versions_startscn,versions_starttime,versions_endscn,versions_endtime,versions_xid,versions_operation,empno
from xyc_t1 versions between timestamp to_timestamp('2013-10-06 10:14:04','YYYY-MM-DD HH24:MI:SS') and to_timestamp('2013-10-06 10:14:23','YYYY-MM-DD HH24:MI:SS');

*/

SQL> select versions_startscn,versions_starttime,versions_endscn,versions_endtime,versions_xid,versions_operation,empno
  2  from xyc_t1 versions between timestamp to_timestamp('2013-10-06 08:17:58','YYYY-MM-DD HH24:MI:SS') and to_timestamp('2013-10-06 08:20:01','YYYY-MM-DD HH24:MI:SS');

VERSIONS_STARTSCN VERSIONS_STARTTIME             VERSIONS_ENDSCN VERSIONS_ENDTIME               VERSIONS_XID     VERSIONS_OPERATION        EMPNO
----------------- ------------------------------ --------------- ------------------------------ ---------------- -------------------- ----------
          1032654              06-OCT-13 08.19.51 AM                                                                                            08000E0016030000       U                                   7788
          1032637              06-OCT-13 08.19.14 AM                                                                                            0600180017030000        I                                    7698
          1032637              06-OCT-13 08.19.14 AM             1032654                06-OCT-13 08.19.51 AM          0600180017030000        I                                    7788
          1032628              06-OCT-13 08.18.47 AM                                                                                            090014002C030000        I                                    7902

--可以看出，一次commit是一个版本，当前版本的versions_endscn和versions_endtime值为空，旧版本则有值。

Flashback Transaction Query闪回事务查询

Flashback Transaction Query实际上是查询的数据字典flashback_transaction_query。可以根据flashback_transaction_query 的undo_sql列值返回数据以前版本。

flashback_transaction_query 列说明：

SQL> desc flashback_transaction_query
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 XID                                                       RAW(8)                 --事务ID
 START_SCN                                          NUMBER                --事务起始SCN，即第一个dml的SCN
 START_TIMESTAMP                             DATE                      --事务其实时间戳,即第一个dm的时间戳
 COMMIT_SCN                                      NUMBER                --提交事务时的SCN
 COMMIT_TIMESTAMP                         DATE                      -- 提交事务时的时间戳
 LOGON_USER                                      VARCHAR2(30)       --本次事务的用户
 UNDO_CHANGE#                                NUMBER                --撤销SCN
 OPERATION                                         VARCHAR2(32)       --执行的dml操作：DELETE,INSERT,UPDATE,BEGIN,UNKNOWN
 TABLE_NAME                                       VARCHAR2(256)     --dml更改的表
 TABLE_OWNER                                     VARCHAR2(32)      --表的所有者
 ROW_ID                                                VARCHAR2(19)       --修改行的ROWID
 UNDO_SQL                                           VARCHAR2(4000)   -‍-撤销dml的sql语句

--使用闪回事务查询前，必须启用重做日志流的其他日志记录，重做日志流与Log Miner使用的数据相同，只是接口不同。

示例说明：

SQL> conn / as sysdba;

SQL> alter database add supplemental log data;

Database altered.

SQL> alter database add supplemental log data (primary key) columns;

Database altered.

SQL> grant select any transaction to scott;

Grant succeeded.

SQL> conn scott/xyc

SQL> update xyc_t1 set sal=9999 where empno=7902;     --更改值sal=9999

1 row updated.

SQL> commit;

Commit complete.

SQL> select to_date(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual;

TO_DATE(SYSDATE,'YY
-------------------
2013-10-06 10:14:04

SQL> update xyc_t1 set sal=99999 where empno=7902;  --更改值sal=99999

1 row updated.

SQL> commit;

Commit complete.

SQL> select to_date(sysdate,'YYYY-MM-DD HH24:MI:SS') from dual;

TO_DATE(SYSDATE,'YY
-------------------
2013-10-06 10:14:23

SQL> select versions_startscn,versions_starttime,versions_endscn,versions_endtime,versions_xid,versions_operation,empno
  2  from xyc_t1 versions between timestamp to_timestamp('2013-10-06 10:14:04','YYYY-MM-DD HH24:MI:SS') and to_timestamp('2013-10-06 10:14:23','YYYY-MM-DD HH24:MI:SS');

VERSIONS_STARTSCN VERSIONS_STARTTIME             VERSIONS_ENDSCN VERSIONS_ENDTIME               VERSIONS_XID     VERSIONS_OPERATION        EMPNO
----------------- ------------------------------ --------------- ------------------------------ ---------------- -------------------- ----------
   1035726                     06-OCT-13 10.14.17 AM                                                                                             0400040097020000 U                                        7902
                                                                                                                                                                                                                                                      7698
                                                                                      1035726                    06-OCT-13 10.14.17 AM                                                                                        7902

--查询事务id

SQL> select start_scn,commit_scn,logon_user,operation,table_name,undo_sql
  2  from flashback_transaction_query
  3  where xid=hextoraw('0400040097020000');

START_SCN COMMIT_SCN LOGON_USER           OPERATION            TABLE_NAME           UNDO_SQL
---------- ---------- -------------------- -------------------- -------------------- --------------------------------------------------
   1035724    1035726           SCOTT                                   UPDATE       XYC_T1               update "SCOTT"."XYC_T1" set "SAL" = '9999' where R
                                                                                                                              OWID = 'AAASNYAAEAAAAIVAAD';

--查出undo sql

SQL> update "SCOTT"."XYC_T1" set "SAL" = '9999' where ROWID = 'AAASNYAAEAAAAIVAAD';

1 row updated.

SQL> select * from xyc_t1;
select * from xyc_t1;

EMPNO ENAME                JOB                       MGR HIREDATE                   SAL       COMM     DEPTNO
---------- -------------------- ------------------ ---------- ------------------- ---------- ---------- ----------
      7698 BLAKE                MANAGER                  7839 1981-05-01 00:00:00       2850                    30
      7902 FORD                 ANALYST                    7566 1981-12-03 00:00:00       9999                    20

--返回到上一版本，即sal值为9999