Mysql left join и sum

Question

У меня есть три стола, и мне нужно сумму отдельно. Также я буду использовать поля в предложении select или where.

SELECT i.*, x.* FROM items AS i 
LEFT JOIN 
(
    SELECT 
    p.item_id 
    ,SUM(p.amount) AS saleAmount 
    ,SUM(IF(p.type=1,pa.amount,0)) AS paidAmount 
    FROM payments AS p 
    LEFT JOIN payment_actions AS pa ON pa.payment_id=p.id 
    GROUP BY p.id 
) AS x ON x.item_id=i.id 

таблица пунктов;

id 
--- 
1 

таблица платежей;

id | item_id | amount 
--------------------------- 
1 | 1  | 300 

таблица платежей_actions;

id | payment_id | amount 
--------------------------- 
1 | 1   | 100 
1 | 1   | 50 

Результат должен быть;

saleAmount | paidAmount 
-------------------------- 
    300  | 150 

Answer 1

Вот простой способ для желаемого результата

SELECT 
    i.id, 
    p.amount, 
    pa.amount 
FROM items AS i 
    LEFT JOIN (SELECT 
      id, 
      item_id, 
      SUM(amount) amount 
     FROM payments 
     GROUP BY item_id) AS p 
    ON p.item_id = i.id 
    LEFT JOIN (SELECT 
      payment_id, 
      sUM(amount) amount 
     FROM payment_actions) AS pa 
    ON pa.payment_id = p.id 
group by i.id