如何将“COUNT”与“GROUP BY”和“WHERE”一起使用

Question

SELECT `loanac`.`id`, `loanac`.`area`
FROM loanac, loantrans
WHERE `loanac`.`lacc`=`loantrans`.`account`
GROUP BY `loanac`.`lacc`
HAVING SUM(IFNULL(`loantrans`.`out`,0)) > SUM(IFNULL(`loantrans`.`in`,0))

查询结果：

----------------------------------------
id      area
----------------------------------------
5       A
165     C
166     C
167     C
232     D
91      B

这个查询给了我所有的 id & area for lacc's who have out> in，这个查询是 OK 和工作的，我只需要从这个查询中得到输出 GROUP BY area 和 COUNT id。有人可以帮忙吗？

我想要的是

----------------------------------------
COUNT(id)      GROUP BY(area)
----------------------------------------
1               A
5               B
9               C
1               D

注意：条件不变 目标：要查找/计数（loanac.id）分组的数量（loanac.area）具有相同的条件

Answer 1

我认为这可以满足您的要求：

SELECT COUNT(id), area FROM
  (SELECT id, area FROM loanac
     JOIN loantrans ON loanac.lacc = loantrans.account
     GROUP BY loanac.lacc
     HAVING SUM(IFNULL(loantrans.out, 0)) > SUM(IFNULL(loantrans.in,0))) t
  GROUP BY area;

在上面，我有一个由loanac.area 组成的组，因为这就是原始示例的样子。如果要按loanac.lacc 分组，只需将上面的GROUP BY 更改为GROUP BY loanac.lacc。

编辑：加载评论中链接的测试数据库并运行查询：

+-----------+------+
| COUNT(id) | area |
+-----------+------+
|        86 | A    |
|        81 | B    |
|        64 | C    |
|        66 | D    |
|        20 | E    |
|         3 | F    |
+-----------+------+

Answer 2

我想你想要这样的东西。将area 添加到您的 GROUP BY 行，并使用 COUNT(id) 获取交易计数。

选择计数（`loanac`.`id`）， SUM(IFNULL(`loantrans`.`out`,0)) 作为转出， SUM(IFNULL(`loantrans`.`in`,0)) 作为转入， `loanac`.`面积`, `loanac`.`lacc` 来自loanac，loantrans WHERE `loanac`.`lacc`=`loantrans`.`account` GROUP BY `loanac`.`lacc`,`loanac`.`area` 有转出>转入

编辑：提供您正在寻找的输出

选择计数（loanac.id），`loanac`.`area` 来自loanac，loantrans WHERE `loanac`.`lacc`=`loantrans`.`account` GROUP BY `loanac`.`lacc`,`loanac`.`area` HAVING SUM(IFNULL(`loantrans`.`out`,0)) > SUM(IFNULL(`loantrans`.`in`,0))