How to exclude rows with duplicate columns?
===

Say I have the following data:

    id1   id2    data
    ----------------------
    7     8      test1
    7     8      test2
    8     7      test1
    8     7      test2

For my needs id1 and id2 can be transposed, so this is essentially duplicate data.  How can I select only one combination of id1/id2 and all of their unique values for `data`?  So desired output would be:

    7   8   test1
    7   8   test2

or

    8   7   test1
    8   7   test2

It really doesn't matter which.