tyarmas-/E1597aS9LQAvxtiuMwx3w@public.gmane.org
2009-Oct-28 11:44 UTC
confused by group_by
I just started using rails and am trying to learn fast but I am confused with what I have read about using group_by and could use some help please. I have two tables - students and evaluations students has many evaluations and evaluations have one student The student record has id, name, and grad_year columns The evaluations record has id, student_id, eval_date and many boolean columns. I would like to get a report of the sum of each of the boolean columns for evaluations by grad_year I would also like to include only items that have a sum > 0 (i.t. if item1 is always false, then sum is zero and it should not be included in the report). I have tried a bunch of things but cannot seem to figure it out. My last attempt was close, but I am not sure if it is best nor what to put in the view to display the actual items. My controller had something like the following (abbreviated to save space): @evaluations = Student.all(:joins => :evaluations, :select "students.*, sum(evaluations.item1) as sum_eval1, sum (evaluations.item2) as sum_item2", :group => "students.grad_year") I can get this query to work in the console, but am not sure how to utilize the results in the view. Thanks, any help is appreciated.