Notes for getting records using rowid and rownum

We know that rowid and rownum can both be used as fake in Oracle and are mainly used to locate specific records in the table, but they are different. rowid is different from row record.

We know that rowid and rownum can both be used as fake in Oracle and are mainly used to locate specific records in the table, but they are different. rowid is different from row record.

In Oracle 8 or lower, rowid (also called restricted rowid) is: FFFF. BBBBBBBB. RRRR, which occupies 6 bytes (10bit file # + 22bit + 16bit). However, to expand the data file, change the rowid to OOOOOOFFFBBBBBBRRR, occupies 10 bytes (32bit + 10bit rfile # + 22bit + 16bit ). Here, O is the Object number, F is the File number, B is the Block number, and R is the Row number. Since the composition of rowid changes from file # To rfile #, the limit on the number of data files cannot exceed 1023 in the entire database, but cannot exceed 1023 data files in each tablespace. The object_id here is an information related to the physical storage location of a segment, because a segment object can only be in one tablespace. object_id can uniquely confirm ts #, object_id + rfile # can finally locate the specified physical data file where the rowid is located.