When a user is generating a where clause for a query, they'd like to retrieve the existing list of values for a particular field and choose amongst them to populate the where clause criteria.

Also offer advanced features where instead of displaying all unique values in the column, I can create a conditional clause such as string > "B" or number < 1000. This lets me restrict the set of unique values that I have to sift through prior to deciding what values to put in my where clause.