MySQL的：從兩列由

Question

類別

組織總計考慮在MySQL數據庫中的以下表：

表1：

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

表2：

+------+-----------+----------------------+ 
| id | budget | category_id | user | 
+------+-----------+--------------|-------+ 
| 1 | 100  | 2   | 1 | 
| 2 | 150  | 1   | 2 | 
| 3 | 50  | 1   | 1 | 
+------+-----------+--------------|-------+ 

表3：

+------+-----------+ 
| id | name | 
+------+-----------+ 
| 1 | one  | 
| 2 | two  | 
| 3 | three | 
+------+-----------+ 

我想計算表1和表2給出了給定用戶（在我的例子中爲1）中'atual'和'budget'的總和，按類別名稱排列：

我試過了下面的查詢，和預算不分類別：

SELECT table2.id, table3.name AS name_category, SUM(budget) , 
(SELECT SUM(atual) FROM table1 WHERE user =1) 
FROM table2 INNER JOIN table3 
ON table2.category_id=table3.id 

Answer 1

這裏有一個方法：

select t3.id, t3.name, sum(actual) as actual, sum(budget) as budget 
from ((select category_id, sum(actual) as actual, NULL as budget 
     from table1 
     where user = 1 
     group by category_id 
    ) union all 
     (select category_id, NULL as actual, sum(budget) as budget 
     from table2 
     where user = 1 
     group by category_id 
    ) 
    ) ab join 
    table3 t3 
    on ab.category_id = t3.id 
group by t3.id, t3.name; 

Answer 2

SELECT t3.id, t3.name AS name_category, SUM(t2.budget) as budgety, SUM(t3.actual) as actual 
FROM table3 t3 
    LEFT OUTER JOIN table1 t1 on t1.category_id=t3.id 
    LEFT OUTER JOIN table1 t2 on t2.category_id=t3.id 
GROUP BY t3.id