如何从MySQL的三个表中获取数据？

我有三个表：产品名称、参数名称和某些产品的参数值：

产品

+-------+-------------+ 
|   id  |  name       |  
+-------+-------------+
|   1   |  A100       |
+-------+-------------+
|   2   |  B250       |
+-------+-------------+

+-------+-------------+ 
|   id  |  name       |  
+-------+-------------+
|   1   |  width      |
+-------+-------------+
|   2   |  color      |
+-------+-------------+

+-------+-----------+-----------+-----------+ 
|   id  |  product  |  param    |  value    |
+-------+-----------+-----------+-----------+ 
|   1   |     1     |    1      |   120     |
+-------+-----------+-----------+-----------+  
|   2   |     1     |    2      |  white    |
+-------+-----------+-----------+-----------+ 
|   3   |     2     |    1      |   275     |
+-------+-----------+-----------+-----------+  
|   4   |     2     |    2      |  black    |
+-------+-----------+-----------+-----------+

参数

+-------+-------------+ 
|   id  |  name       |  
+-------+-------------+
|   1   |  A100       |
+-------+-------------+
|   2   |  B250       |
+-------+-------------+

+-------+-------------+ 
|   id  |  name       |  
+-------+-------------+
|   1   |  width      |
+-------+-------------+
|   2   |  color      |
+-------+-------------+

+-------+-----------+-----------+-----------+ 
|   id  |  product  |  param    |  value    |
+-------+-----------+-----------+-----------+ 
|   1   |     1     |    1      |   120     |
+-------+-----------+-----------+-----------+  
|   2   |     1     |    2      |  white    |
+-------+-----------+-----------+-----------+ 
|   3   |     2     |    1      |   275     |
+-------+-----------+-----------+-----------+  
|   4   |     2     |    2      |  black    |
+-------+-----------+-----------+-----------+

paramsofproducts

+-------+-------------+ 
|   id  |  name       |  
+-------+-------------+
|   1   |  A100       |
+-------+-------------+
|   2   |  B250       |
+-------+-------------+

+-------+-------------+ 
|   id  |  name       |  
+-------+-------------+
|   1   |  width      |
+-------+-------------+
|   2   |  color      |
+-------+-------------+

+-------+-----------+-----------+-----------+ 
|   id  |  product  |  param    |  value    |
+-------+-----------+-----------+-----------+ 
|   1   |     1     |    1      |   120     |
+-------+-----------+-----------+-----------+  
|   2   |     1     |    2      |  white    |
+-------+-----------+-----------+-----------+ 
|   3   |     2     |    1      |   275     |
+-------+-----------+-----------+-----------+  
|   4   |     2     |    2      |  black    |
+-------+-----------+-----------+-----------+

如何通过一次查询得到该表（所有产品+参数作为列）？我不能用JOIN做这件事

+-------+----------+-----------+-----------+ 
|   id  |  name    |  width    |  color    |
+-------+----------+-----------+-----------+ 
|   1   |  A100    |   120     |  white    |
+-------+----------+-----------+-----------+ 
|   2   |  B250    |   275     |  black    |
+-------+----------+-----------+-----------+

---

我无法提供您想要的结果，但您的结果中是否有JSON可能是一种解决方法：

SELECT products.id, products.name, CONCAT('[{',GROUP_CONCAT('"',REPLACE(params.name,  '"', '\\"'),'":"', REPLACE(paramsofproducts.value, '"', '\\"'),'"'),'}]') as params
FROM paramsofproducts 
LEFT JOIN products ON products.id = paramsofproducts.product 
LEFT JOIN params ON params.id = paramsofproducts.param
GROUP BY products.name

结果:

id | name | params
1  | A100 | [{"width":"120","color":"white"}]
2  | B250 | [{"width":"275","color":"black"}]

---

编辑：转义“

您可以构造透视表查询，但我的首选项（尤其是属性[

params

]的数量未知时）只是返回一个分组有序的结果，并处理表示层/应用程序级代码中的格式设置。此外，

paramsofproducts

表中的id列可能毫无意义-我们不要对常见问题进行升级，为什么不能使用

连接来实现这一点？您需要转义一些引号以获得有效的JSON在所有情况下。谢谢，这是个好主意，但我不能按参数对这个表进行排序。因此，我必须获取数据并在PHP中创建一个排序数组。