How to get the value of a field in one record in to the other record?

                            Field1       Field2         Field3
(Record #1)          11               ABC            ABC           
(Record #2)          11                                  ABC
(Record #3)          12               GHI             GHI
(Record #4)          12                                  GHI


In the above table, I have 3 fields. Field1 is ID(or any numeric field), Filed2 is a text Field.

I need Field3 to be showing ABC in the record 1 and Record 2. and GHI in record 3 and Record 4.

To rephrase the same question. I need the Field 3\record 2 should be fetching the value from Field2\record 1.

Please Help me.