>Is it possible to create an index tag on a field that would enforce unique entry in the field, unless the entry is blank (no entry)?
INDEX ON MyField FOR NOT ISBLANK(MyField) TAG tttt CANDIDATE
BUT such indexes can't be used in optimization.
Against Stupidity the Gods themselves Contend in Vain - Johann Christoph Friedrich von Schiller
The only thing normal about database guys is their tables.
