- ROWID is a semi-physical value specifying the location of a row (in terms of data file, extent, etcetera). ROWID is not very useful in day-to-day programming, as it is not a constant value (it changes with table re-organizations, imports, and things like that). Therefore it requires caution in its use. - ROWNUM is a logical value for the sequence of row retrieval in the resultset. This is the position before sorting, so rownum is not always the same as the position in the resultset presented to you. This also requires some caution.
Hope this helps,
subject: Difference between rowid and rownum in sql query??