How can I compare rows from 2 tables that have composite primary keys?

Question

Here's the scenario:

I have 2 tables with data, one is the 2009 version and the other is the 2010 version. The primary key for each of the tables is a composite key. I know there is a different number of rows in each one and I need to find out the differences.

Typically, in the "normal" primary key set-up, I would just look for primary key values NOT IN the list of primary keys from the other table. But I don't know how to do this with a composite primary key (or even if it's possible).

So, how can I compare the rows from these two tables?

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EDIT: More specifically, I am trying to find the difference between the tables, rather than the rows in common

Answer 1

Just make a full outer join with condition based on your composite keys:

select t09.*, t10.*
from table2009 as t09
  full outer join table2010 as t10
    on t09.k1 = t10.k1 and t09.k2 = t10.k2 and ...

If you only wish to see unmatched rows (the difference) in result set, then filter them within the where clause:

where t09.k1 is null or t10.k1 is null