query: SELECT name FROM enzyme WHERE product != 'Heme'
question: What-all the names of enzymes whose product is not Heme one ''?
query_toks: SELECT name FROM enzyme WHERE product ! = 'Heme '
query_toks_no_value: select name from enzyme where product ! = value
question_toks: What-all the names of enzymes whose product is not Heme one ''?