Oracle：加载日期时间

Question

I need to extract some data from an Oracle table that was loaded on a particular day. Is there a way to do that? The rows do not have any datetimestamp entry

Answer 1

Found it - ORA_ROWSCN. Have to figure out how to convert it to a date (SCN_TO_TIMESTAMP is not working)

Answer 2

In general, no. You'd need a date column in the table.

If the load was recent, you could try

select scn_to_timestamp( ora_rowscn ), t.*
  from table t

However, there are several problems with this

• Oracle only knows how to convert recent SCN's to timestamps (on the order of a few days). You probably would need to create a new function that called scn_to_timestamp and handled the exception if the SCN can't be converted to a timestamp.
• The conversion of an SCN to a timestamp is approximate (should be within a minute)
• Unless the table was built with rowdependencies (which is not the default), the SCN is stored at the block level not at the row level. So if your load changed one row in the block, all the rows in the block would have the same updated SCN. If you can tolerate picking up some rows that were loaded earlier and/or you know that your load only writes to new blocks, this may be less of an issue.

Beyond that, you'd be looking at things like whether flashback logs were enabled or some other mechanism was in place to track data versioning.