2194 Unable to perform DISTINCT operation on some of the columns

Advantage Error Guide

Problem: The DISTINCT operation cannot be performed on some columns in the result set. DISTINCT operation will fail if the query contains any of the following column types in the result set: character or binary columns that are larger than 1 KB, or MEMO, BLOB, or VARCHAR columns.

Solution: Adjust the SELECT list so it does not include any offending column.