將一個基於結果的組中兩個不同表的兩列按另一表的 ID 求和

Question

我有3張桌子：

用戶：

id                 | account_name
-------------------|----------------------|
18                 | panic                |

存款：

id                 | user_id     | amount
-------------------|---------------------------|
1                  | 18          | 100          
2                  | 18          | 100          

提款：

id                      | user_id          | amount
------------------------|--------------------------------|
1                       | 18          | 200          
2                       | 18          | 200          

我正在嘗試獲得如下結果：

id                      | totalDeposits  | totalWithdraws
------------------------|---------------------------|
18                      | 200            | 400          

現在，當我出於某種原因嘗試獲取總數時，它們會交叉相加，當然，如果沒有行，它應該返回 0。

SELECT t0.id,IFNULL(SUM(t1.amount),0) AS totalWithdrawals,
IFNULL(SUM(t2.amount),0) AS totalDeposits
FROM users t0 
LEFT OUTER JOIN withdrawals t1 ON (t0.id = t1.user_id) 
LEFT OUTER JOIN deposits t2 ON (t0.id = t2.user_id) 
GROUP BY t0.id

知道如何進行這種交叉連接或我在哪里總結錯誤嗎？

Answer 1

嘗試這個-

SELECT A.id,
(SELECT SUM(amount) FROM Deposits WHERE user_id = A.id) totalDeposits, 
(SELECT SUM(amount) FROM Withdrawals WHERE user_id = A.id) totalWithdraws 
FROM users A
WHERE A.id = 18 -- WHERE can be removed to get all users details

Answer 2

你可以嘗試一些類似的東西

SELECT u.id, 
       COALESCE(d.amount, 0) totalDeposits,
       COALESCE(w.amount, 0) totalWithdrawals
  FROM users u
  LEFT JOIN (
    SELECT user_id, SUM(amount) amount 
      FROM deposits 
     GROUP BY user_id
  ) d ON u.id = d.user_id
  LEFT JOIN (
    SELECT user_id, SUM(amount) amount 
      FROM withdrawals 
     GROUP BY user_id
  ) w ON u.id = w.user_id

SQLFiddle

結果：

| id | totalDeposits | totalWithdrawals |
|----|---------------|------------------|
| 18 |           200 |              400 |

Answer 3

問題是您正在生成笛卡爾積。 一種解決方案是先聚合。 另一種方法是使用UNION ALL和GROUP BY 。 我會將其結構為：

SELECT u.id,
       SUM(deposit) as deposits,
       SUM(withdrawal) as withdrawal
FROM users u LEFT JOIN
     ((SELECT d.user_id, d.amount as deposit, 0 as withdrawal
       FROM deposits d
      ) UNION ALL
      (SELECT w.user_id, 0, w.amount 
       FROM withdrawals w
      )
     ) dw
     ON u.id = dw.user_id
GROUP BY u.id;