MySQL 对两个表进行联接和求和

Question

I'm trying to join two tables and sum the results from both tables columns but I can't figure out. I'm doing it in Joomla.

invoices table:

id	owner	amount
1	123	300.00
2	123	125.00
3	144	200.00
4	166	155.00

expenses table:

id	owner	amount
1	123	10.00
2	123	50.00
3	144	50.00

results:

owner	invoices	expenses
123	425.00	60.00
144	200.00	50.00
166	155.00	0.00

Answer 1

This should give you the expect results. I do LEFT JOIN for results from both tables.

SELECT l.`owner`, invoices, IFNULL(expenses,0) FROM
(
  SELECT 
    `owner`, SUM(amount) AS invoices
  FROM
    invoices
  GROUP BY
    `owner`
) AS l LEFT JOIN (
  SELECT 
    `owner`, SUM(amount) AS expenses 
  FROM
    expenses
  GROUP BY
    `owner`
) AS r ON l.`owner` = r.`owner`