Question

I have accounts which have category associated with it & orders table where order can be either debt or credit based on “order_type” field & a payment table which stores the date of payment along with the amount (no negative numbers used for debt or credits).

currently I am using something like this:

SELECT cat, SUM(p.amount) balance
FROM accounts a 
LEFT JOIN orders o ON a.id = o.account_id
LEFT JOIN payments p ON o.id = p.order_id
WHERE YEAR(p.date) = 2012
GROUP BY a.cat

The first issue:

This would count all as paid-in money which is wrong, I’ve tried to use

sum(IF(o.order_type = 1, p.amount, p.amount * -1 ))

which failed to give me correct result as all amounts were negative.

Second issue:

It won’t show categories where no payments were made, the limiting factor here is the date which I need to make sure that I am counting payments on 2012 only but I also want to show all categories with zeros if no payments were made.

Am I approaching it the WRONG way?

If anyone knows a solution for either issues or both, please provide your solution on this.

Answer 1

SELECT cat, SUM(p.amount) balance
FROM accounts a 
LEFT JOIN orders o
  ON a.id = o.account_id
     AND o.order_type = 1
LEFT JOIN payments p
  ON o.id = p.order_id
     AND YEAR(p.date) = 2012
GROUP BY a.cat

The year check has to be in the JOIN condition, not WHERE, so it won’t exclude the categories with no payments.