Question

我试图创建一个基本上等于此的查询（不起作用）。

SELECT * FROM `categories` AS C AND
SELECT * FROM `items` AS I AND
SELECT COUNT(I.id) AS items AND
SELECT SUM(I.price) AS price;

我没有使用SQLServer，而且我通过PHP使用PDO进行数据库连接。

这是表格。

分类

+----+------------+
| id |  Category  |
+----+------------+
|  1 | First_Cat  |
|  2 | Second_Cat |
+----+------------+

项

+----+----------+------+-------+
| id | category | name | price |
+----+----------+------+-------+
|  1 |        1 | Foo  | 1.99  |
|  2 |        1 | Bar  | 2.00  |
|  3 |        2 | ooF  | 0.99  |
|  4 |        2 | raB  | 1.99  |
+----+----------+------+-------+

基于这些表格，我期待这些查询结果：

+----+------------+-------+-------+--+
| id |  category  | items | price |  |
+----+------------+-------+-------+--+
|  1 | First_Cat  |     2 | 3.99  |  |
|  2 | Second_Cat |     2 | 2.98  |  |
+----+------------+-------+-------+--+

有任何帮助吗？

Answer 1

您在评论中发布的查询未加入类别表和项目表。这让我觉得你可以做这样的事情吗？：

SELECT 
    categories.id,
    categories.Category,
    COUNT(*) AS items,
    SUM(items.price) as price
FROM 
    `categories`
    JOIN items
        ON categories.id = items.category
GROUP BY
    categories.id,
    categories.Category

基本的SQL查询设计问题

1 个答案: