Are you trying to update a record's Primary Key to equal an existing value? Does your database allow any unique constraints on non-key fields? If so, are you breaking that rule by trying to update a field to an existing value?
Are you trying to update a record's Primary Key to equal an existing value? -- Yes
A Primary Key identifies a tuple (a record). If you change the identifier of a tuple, this is analagous to doing an insert, not an update, since a tuple with a different identifier equals a different tuple. If this is what you want to do, you should really delete the first tuple and insert its replacement.
Does your database allow any unique constraints on non-key fields? -- The db is Oracle, so I would say yes
You are right, it does. In which case you should check your table's DDL ("desc <tablename> " in SQLPlus, or look at it through Enterprise Manager) and see if there are any on the table you are trying to update. If there are you will have to check that you are not violating the constraint before trying to update a tuple. Which you can do with a select statement.
If I have 15 columns (2 are primary keys), and I try to update with all the same data, I will get this error?
You cannot define more than one Primary Key in a table. You may have a Composite Key, which has two identifying fields. Taken together they would define the Primary Key.
It sound like you may be a little shakey on constraints. You might benefit from reading the chapter of the Oracle documentation "Database Concepts: Data Integrity". [ June 15, 2005: Message edited by: Paul Sturrock ]