Based on your example, I think this query could do the trick, but the subquery will perform a full table scan (as the main query), unless an index exists on (colB,colC).
<pre>select * from test t
where not exists
(select 1 from test where colB = t.colB + 0.01 and colC = t.colC + 0.01);</pre>
You did not specify what database are you using, so the syntax may need some changes.
The same result could be accomplished using an outer join (this is oracle syntax, so please make the necessary changes):
<pre>select * from test t, test t2
where t.colB+0.01 = t2.colB(+)
and t.colC+0.01 = t2.colC(+)
and t2.colB is null</pre>
Hope this helps.