Using Case statement in sqlite, trouble getting the results I'm looking for

Question

I am having difficulty with a SQL query. I'm using sqlite.

I have a table expenses . I'm trying to use a CASE statement to select and sum values. Here's some sample data:

This is the query which is not getting what I'd like...

SELECT e.category, 
  CASE 
    WHEN e.schedule ='None' AND e.created_at > '2014-02-01 00:00:00 +0000' THEN SUM(e.amount) 
    WHEN e.schedule = 'Daily' THEN SUM(e.amount)*28.000000 
    WHEN e.schedule = 'Mon - Fri' THEN SUM(e.amount)*20 
    WHEN e.schedule = 'Weekly' THEN SUM(e.amount)*4.000000 
    WHEN e.schedule = 'Every 4 Weeks' THEN SUM(e.amount)*1.083333333333 
    WHEN e.schedule = 'Monthly' THEN SUM(e.amount)*1 
  ELSE 0 
  END 
AS totalValue FROM expenses e GROUP BY e.category ORDER BY e.category

Below is a pic of what the query returns.

What I would like to see in total value for Housing 420, this is because there is are three records with the category "Housing", one of which has a schedule of "None" (record id 2) and was created in January. The other two (records 10 and 16) have a schedule of Monthly. In my CASE I try to only select the schedules with a created_at greater than the 1st of Feb:

    WHEN e.schedule ='None' AND e.created_at > '2014-02-01 00:00:00 +0000' THEN SUM(e.amount)

Or with a schedule value other than "None", in this case:

    WHEN e.schedule = 'Monthly' THEN SUM(e.amount) 

Unfortunately I'm getting a result of 495 (300 + 120 + 75). It's summing all the records with a particular category if it finds a record that fits the case statement!

Please can you help me rewrite the case so that I get the results I'm looking for.

Answer 1

One problem with the query is that you are using e.schedule in the select list but it is not in a group by . This is usually the sign of a problem.

I think you want to move the entire case statement inside the sum() :

SELECT e.category, 
       SUM(CASE WHEN e.schedule ='None' AND e.created_at > '2014-02-01 00:00:00 +0000' THEN e.amount
                WHEN e.schedule = 'Daily' THEN e.amount*28.000000 
                WHEN e.schedule = 'Mon - Fri' THEN e.amount*20 
                WHEN e.schedule = 'Weekly' THEN e.amount*4.000000 
                WHEN e.schedule = 'Every 4 Weeks' THEN e.amount*1.083333333333 
                WHEN e.schedule = 'Monthly' THEN e.amount*1 
                ELSE 0 
           END) as totalValue
FROM expenses e
GROUP BY e.category
ORDER BY e.category;

Otherwise, you might want to move e.schedule to the group by clause to have a separate row for each schedule within each category.