Database: allergy_1
Question: Find the number of students who are older than 18 and do not have allergy to either food or animal.
SQL: select count(*) from student where age  >  18 and stuid not in ( select stuid from has_allergy as t1 join allergy_type as t2 on t1.allergy  =  t2.allergy where t2.allergytype  =  "food" or t2.allergytype  =  "animal")