错误：除以零 + PostgreSQL + Rails

Question

I'm getting the following error when I run this database view in psql (ERROR: division by zero). Even I can't access my table in rails console If anyone has any solution for this error so please comment on it will be very helpful thanks in advance.

select 
      (exam_id || '00' || quarter)::bigint as id,
      account_id,
      exam_id,
      quarter,
      quarter_label,
      count(id) as assessments,
      max(banding_percentage) as top_assessment_percentage,
      min(banding_percentage) as bottom_assessment_percentage,
      round(avg(banding_percentage),2) as avg_assessment_percentage
    from report_assessments
    group by account_id, exam_id, quarter, quarter_label;

Answer 1

To avoid running into division by zero exceptions you should use nullif , so that you can catch this 0 and replace it by null , eg

WITH j (v1,v2) AS (
  VALUES (1.0,0.0),(10.0,3.0)
) 
SELECT v1/nullif(v2,0) AS div FROM j;

        div         
--------------------

 3.3333333333333333
(2 Zeilen)

Answer 2

You Need to do something like this. It works in my case:

Negotiation.find(
  :all, 
  conditions: conditions_hash('negotiation'),
  select: 
    'CASE 
      sum(banding_percentage) 
      WHEN 
        0 
      THEN 
        NULL 
      ELSE 
        sum(total_percentage) / sum(banding_percentage) 
      END as error_check'
).first