1
products(id, name)
categories(id, name, product_id)

我有一个示例代码:

products(1, 'Apple')

和类别

categories(1, 'Iphone', 1)
categories(2, 'Ipad', 1)
categories(3, 'Ipod', 1)

并查询:

SELECT pr.id, cat.name, pr.name 
FROM `products` as pr
LEFT JOIN `categories` as cat USING(id)
GROUP BY pr.id

但结果是

1, "Iphone", "Apple"

而且Ipad, Ipod不显示,如何解决?

 1, "Iphone, Ipad, Ipod", "Apple"
4

1 回答 1

2

您的 JOIN 条件正在尝试连接两个 ID 列,这不是关系。它应该将 product.id 加入 category.produt_id

SELECT pr.id, cat.name, pr.name 
FROM `products` as pr
LEFT JOIN `categories` as cat ON pr.id = cat.product_id
GROUP BY pr.id

编辑:我意识到你只想要一个连接类别的结果。您需要选择列表中的 GROUP_CONCAT 函数:

SELECT pr.id, GROUP_CONCAT(cat.name), ...

http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat

于 2012-06-18T02:02:50.330 回答