+ AA6YQ comments below

Nope, that doesn't work.  It returns no errors, just no entries.  Typing RCC in the filter box and clicking the Tags buton returns 4 entries. 

Backing up a step, I've got all the callsigns entered in the Callsign field and RCC in the Tag List field.  Seems correct, it works with the pre-defined button.

+ Use this SQL expression:

TAGS LIKE '*RCC*'

      73,

             Dave, AA6YQ