query: SELECT Allergy ,  count(*) FROM Has_allergy GROUP BY Allergy
question: How students many has each allergy different?
query_toks: SELECT Allergy , count ( * ) FROM Has_allergy GROUP BY Allergy
query_toks_no_value: select allergy , count ( * ) from has_allergy group by allergy
question_toks: How students many has each allergy different?