Question

I’m working out a query that I’ve ran successfully in MySQL for a while, but in Postgres it’s not working with the ole –

ERROR:  column "orders.created_at" must appear in the GROUP BY clause 
or be used in an aggregate function

Here’s the query:

SELECT SUM(total) AS total, to_char(created_at, 'YYYY/MM/DD') AS order_date 
FROM orders 
WHERE created_at >= (NOW() - INTERVAL '2 DAYS') 
GROUP BY to_char(created_at, 'DD') 
ORDER BY created_at ASC;

It’s just supposed to return something like this:

  total  | order_date 
---------+------------
 1099.90 | 2013/01/15
  650.00 | 2013/01/16
 4399.00 | 2013/01/17

The main thing is I want the sum grouped by each individual day of the month.

Anyone have ideas?

UPDATE:

The reason I’m grouping by day is because the graph will be labeled with each day of the month, and the total sales for each.

1st - $3400.00
2nd - $2237.00
3rd - $1489.00

etc.

Answer 1

I’m not sure why you’re doing a conversion there. I think the better thing to do would be this:

SELECT 
  SUM(total) AS total, 
  created_at::date AS order_date 
FROM 
  orders 
WHERE 
  created_at >= (NOW() - INTERVAL '2 DAYS') 
GROUP BY 
  created_at::date 
ORDER BY 
  created_at::date ASC;

I would recommend this query and then format the daily labels in your graph through the graph settings to ensure you do not have any weird issues of the same day in different months getting grouped. However, to get what you display in your edit you can do this:

SELECT 
  SUM(total) AS total, 
  to_char(created_at, 'DDth') AS order_date 
FROM 
  orders 
WHERE 
  created_at >= (NOW() - INTERVAL '2 DAYS') 
GROUP BY 
  to_char(created_at, 'DDth') 
ORDER BY 
  to_char(created_at, 'DDth') ASC;