Question

I recently learnt that oracle has a feature which was pretty useful to me – as the designer/implementator didn’t care much about data history – I can query the historical state of a record if it’s available yet in the oracle cache, like this:

select *    from ( select *             from sometable where some_condition )  as of timestamp sysdate-1  

But now I need to check the historical data within a range. Is it possible anyhow, using the cache?

Answer 1

Yes, like this:

SQL> select sal from emp where empno=7369;         SAL ----------       5800  SQL> update emp set sal = sal+100 where empno=7369;  1 row updated.  SQL> commit;  Commit complete.  SQL> update emp set sal = sal-100 where empno=7369;  1 row updated.        SQL> commit;  Commit complete.  SQL> select empno, sal, versions_starttime,versions_xid   2  from emp   3  versions between timestamp sysdate-1 and sysdate   4  where empno=7369;       EMPNO        SAL VERSIONS_STARTTIME                                                          VERSIONS_XID ---------- ---------- --------------------------------------------------------------------------- --       7369       5900 11-DEC-08 16.05.32                                                          0014001300002A74       7369       5800 11-DEC-08 16.03.32                                                          000D002200012EB1       7369       5800 

Note that how far back you can go is limited by the UNDO_RETENTION parameter, and will typically be hours rather than days.