Question

我正在尝试连接几个表格，下面是布局示例：

订单

user_id=7 pricing id=37

products_pricing

id=37 product_id=33

产品

id=33 name=test product

SQL

SELECT *
FROM orders
  INNER JOIN products_pricing
    ON orders.pricing_id = products_pricing.id
  INNER JOIN products
    ON products_pricing.product_id = products.id
WHERE orders.user_id = '7' ");

选

id=233 user_id=7 url=test.com

使用这个SQL我得到一个输出，给我user_id为7的所有产品，它将在while循环中列出每个产品名称。然而，当我为一个名为listing的表添加另一个INNER JOIN时，它有一个user_id列，我需要为匹配的每一行抓取一个url，所以我可以用url超链接产品名称，我也可以获得列表中包含的所有内容作为上面的工作内容。我要么做得非常错，要么错过了什么。我花了几个小时试图找出它，但一直得到相同的结果。任何人都可以帮助我吗？

Answer 1

试试这个：

SELECT 
  p.id,
  p.name,
  l.url,
  o.user_id,
  o.pricing_id
FROM orders AS o
INNER JOIN products_pricing AS pp ON o.pricing_id  = pp.id
INNER JOIN products         AS  p ON pp.product_id = p.id
INNER JOIN listings         AS  l ON l.user_id = o.user_id
WHERE o.user_id ='7' 
  AND l.id = 233 
  AND l.url = 'test.com';

SQL Fiddle Demo

对于您在问题中发布的样本数据，这将为您提供：

| ID |        NAME |      URL | USER_ID | PRICING_ID |
------------------------------------------------------
| 33 | testproduct | test.com |       7 |         37 |

Answer 2

是的，这可以使用INNER join本身完成。并在select语句中获取select列。

SELECT 
  p.id,
  p.name,
  l.url,
  o.user_id,
  o.pricing_id
FROM orders AS o
INNER JOIN products_pricing AS pp ON o.pricing_id  = pp.id
INNER JOIN products         AS  p ON pp.product_id = p.id
INNER JOIN listings         AS  l ON l.user_id = o.user_id
WHERE o.user_id ='7' 
  AND l.id = 233 
  AND l.url = 'test.com';

MySQL内部连接查询多个表

2 个答案:

SQL Fiddle Demo