title: Query with Join and calculation
body: <p>I need to create a query based on the following question:</p>
  
  <p>I need to add the number of instructors and students that have the same zip and if it is more than 10 then list the city, state, total number of instructors, total number of students, and the total from adding the instructors and students together.
  All three tables have the zip field that they share. It is the primary key in the zipcode table and a foreign key in the instructor and student table. The city and state fields are in the zipcode table. I initially had this query but no rows are returned. I can't get the total. Every time I incorporate either SUM or addition I get a ORA 00923 From keyword not found where expected error.</p>
  
  <pre><code>select city, state, 'TOTAL'
  from zipcode
  left join
  (select student.zip, count(*) 'Total_Stud'
  from student
  group by zip)
  s on zipcode.zip=student.zip
  left join
  (select instructor.zip, count(*) 'Total_Inst'
  from instructor
  group by zip)
  i on zipcode.zip=instructor.zip
  where count(student.student_id) + count(instructor.instructor_id)&gt;=10 as total
  order by total desc;
  </code></pre>
  
  <p>There are 3 tables involved
  Student Table, instructor and zipcode</p>