In this case, "keyword" is from a LabKey defined table, and can not be null. I wouldn't have expected there to be any empty strings, but we must have read an FCS file that had an empty keyword name. Weird. My recommendation is the same as Ben's using col != '' in SQL should work. I'm not sure we have a LABKEY.Filter way to express that since we try not to use empty strings because it's too confusing.

Matt