MySQL Sum positive and negative - calculate the exact total from money transactions

Question

I have a database table full of transactions. The transactions contain negative numbers from people returning items. I would like to add up all the amount field while also subtracting the negative values of returns from the total. How can I do this and output it out? Currently the best I can do is get:

  SELECT SUM(amount) 
  FROM outputaddition 
  GROUP by SIGN(amount);

But this only puts positive and negative in the same column.

Answer 1

SELECT personId,SUM(CASE WHEN amount<0 THEN amount ELSE 0 END) as NegativeTotal,
       SUM(CASE WHEN amount>=0 THEN amount ELSE 0 END) as PostiveTotal
FROM outputaddition
GROUP BY personID

If you want single column

SELECT personId,SUM(amount) as Total
FROM outputaddition
GROUP BY personID