Question

在MySQL中，我必须查询两个表：

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    |
+------+------------+-------+

我想获取用户1的总数。

这两张表没有关系。但是，它们具有共同的用户密钥。

这就是我的尝试：

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

产生错误：

#1630 - FUNCTION SUM does not exist.

Answer 1

您需要在join：

之前进行汇总

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

编辑：

当你在一个问题中说“这两个表不相关”时，你肯定不关心用户列。我想你真的想要这个：

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

Answer 2

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

Answer 3

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

MySQL查询：从两个不相关的表中获取总计

3 个答案: