Question

我正在学习CTE，却陷入了一项运动中。请查看下表：

捐赠

    +----+------------+--------------+---------+------------+------------+
    | id | project_id | supporter_id | amount  | amount_eur | donated    |
    +----+------------+--------------+---------+------------+------------+
    | 1  | 4          | 4            | 928.40  | 807.70     | 2016-09-07 |
    | 2  | 8          | 18           | 384.38  | 334.41     | 2016-12-16 |
    | 3  | 6          | 12           | 367.21  | 319.47     | 2016-01-21 |
    | 4  | 2          | 19           | 108.62  | 94.50      | 2016-12-29 |
    | 5  | 10         | 20           | 842.58  | 733.05     | 2016-11-30 |
    | 6  | 4          | 15           | 653.76  | 568.77     | 2016-08-05 |
    +----+------------+--------------+---------+------------+------------+

项目

+----+------------+-----------+----------------+
| id | category   | author_id | minimal_amount |
+----+------------+-----------+----------------+
| 1  | music      | 1         | 1677           |
| 2  | music      | 5         | 21573          |
| 3  | travelling | 2         | 4952           |
| 4  | travelling | 5         | 3135           |
| 5  | travelling | 2         | 8555           |
+----+------------+-----------+----------------+

支持者

+----+------------+-----------+
| id | first_name | last_name |
+----+------------+-----------+
| 1  | Marlene    | Wagner    |
| 2  | Lonnie     | Goodwin   |
| 3  | Sophie     | Peters    |
| 4  | Edwin      | Paul      |
| 5  | Hugh       | Thornton  |
| 6  | Dianne     | Harris    |
+----+------------+-----------+

目的是显示支持者的名字和姓氏，以及尚未建立的项目的数量（金额的总和< minimal_amount ），他们创建了。

我的SQL：

WITH projects AS
( 
    SELECT 
        first_name AS firstName,
        last_name AS lastName,
        project_id,
        SUM(amount) AS amountSum,
        minimal_amount
    FROM 
        donation d
    INNER JOIN 
        project p ON p.id = d.project_id
    INNER JOIN 
        supporter s ON s.id = p.author_id
    GROUP BY 
        FIRST, LAST, project_id
)
SELECT 
    firstName,
    lastName,
    COUNT(project_id)
FROM 
    projects
WHERE 
    amountSum < minimal_amount;

我遇到一个错误：

“第一”列不存在

Answer 1

您错误地在GROUP BY FIRST中提到了列名，而LAST在您的表中不存在，并且minimal_amount也需要包含在group by子句中，因为您没有对该列使用任何汇总

    WITH projects AS
      ( 
       SELECT first_name AS firstName,
               last_name AS lastName,
               project_id,
               sum(amount) AS amountSum,
               minimal_amount
       FROM donation d
       INNER JOIN project p ON p.id = d.project_id
       INNER JOIN supporter s ON s.id = p.author_id
       GROUP BY first_name ,
                last_name ,
                project_id,minimal_amount
)
    SELECT firstName,
           lastName,
           count(project_id)
    FROM projects
    WHERE amountSum < minimal_amount
   group by firstName,
           lastName

CTE查询失败，并显示有关未知列名的错误

1 个答案: