Question : update one date field with another, for the same key

Experts,

I have a temporary table filled with history data from the source.  Ultimately I need to load it to a real table, but only after I figure something out.  I have multiple records per class ( rtclas ), but they are distinct when you factor in effective_date ( which is rtmnth, rtday, and rtyear concatenated ) and rate indicator ( rtrind ).  There can be an A, B, and C indicator for each rtclas and effective_date.  Now comes the fun part.  I need to populate the expiration_date with the effective_date of the next record ( meaning next effective_date ) with the same rtclas.  I think if 3 records have the same rtclas and effective_date ( meaning the rtrind or rate indicator comes into play - with values of A, B, and/or C ) then all three of them ( for example ) would have the same expiration_date.  Once we have reached the last record in that rtclas ( meaning that if we were looking at the file sequentially by rtclas, the next record would have a different rtclas ), then the expiration_date for that record would be 12/31/2078.  I am putting the data from this table into a spreadsheet, which I will attach for your review.  For example:
                                                                                           
RTCLAS          EFFECTIVE_DATE               RTRIND             EXPIRATION_DATE
-----------         ----------------------             ------------          ------------------------
5                          10/1/1995                             A                         1/1/1996
5                            1/1/1996                             A                          1/1/1997
5                            1/1/1997                             A                         12/31/2078
5                            1/1/1997                             B                          12/31/2078
5                            1/1/1997                             C                          12/31/2078
6                            7/1/2000                             A                           7/1/2002    
6                            7/1/2002                             A                              ETC.

I understand ( or am guessing ) that there should be grouping in this and perhaps ordering, but I am not quite sure how to do it.  I was thinking of putting some of the grouped data into another temp. table to ultimately query off that, but I am not certain.  Please understand I am pretty much a novice in Oracle, so if we could use the simplest method to get the result set I am looking for, I would appreciate it.  Thanks so much.

Scott

Answer : update one date field with another, for the same key

I would think a 2 step process would do it.

The first would be to update the expiration dates of all the records that can be updated:

update a
     set expiration_date = (select min(effective_date)
                                           from b
                                         where a.rtclas = b.rtclas and
                                                    a.rtrind = b.rtrind and
                                                    b.effective_date > a.effective_date);

The second would be to update the "last" records, which would be the remaining ones:

update
  set expiration_date = to_date('12312078','mmddyyyy')
where expiration_date is null;