MySQL查詢：從兩個非關聯表

Question

在MySQL中獲取總計，我要查詢兩個表：

表1：

+------+-----------+-------+ 
| id | atual | user | 
+------+-----------+-------+ 
| 1 | 100  | 1 | 
| 2 | 150  | 1 | 
| 3 | 50  | 2 | 
+------+-----------+-------+ 

表2：

+------+------------+-------+ 
| id | budget | user | 
+------+------------+-------+ 
| 1 | 80  | 3 | 
| 2 | 150  | 1 | 
| 3 | 200  | 2 | 
+------+------------+-------+ 

我要搶用戶1的總數。

兩個表格不相關。不過，他們擁有共同的用戶密鑰。

這是我的嘗試：

SELECT SUM(atual), SUM(budget) 
FROM table1, table2 
WHERE user=1 

這是產生錯誤：

#1630 - FUNCTION SUM does not exist. 

Answer 1

SELECT SUM(atual), 
    (SELECT SUM(budget) FROM table2 WHERE user=1) 
FROM table1 
WHERE user=1 

Answer 2

SELECT SUM(table1.atual) as Actual, SUM(table2.budget) as Budget 
FROM table1, table2 
WHERE table1.user=1 

Answer 3

您需要join之前做了彙總：

select a.actual, b.budget 
from (select sum(actual) as actual from table1) a cross join 
    (select sum(budget) as budget from table2) b; 

編輯：

當你在一個問題中說「兩個表格不相關」時，它肯定會顯示你不關心用戶列。我覺得你真的想這樣：

select user, sum(actual) as actual, sum(budget) as budget 
from ((select user, sum(actual) as actual, NULL as budget 
     from table1 
     group by user 
    ) union all 
     (select user, NULL as actual, sum(budget) as budget 
     from table2 
     group by user 
    ) 
    ) ab 
group by user