Question

使用PHP / MySQL

我有两个表，一个是customers，另一个是cust_data

有一个字段匹配ListID

这两个字段

现在在cust_data表中，数据列为cust_data

列：

ListID  DataName  DataValue
 1      type      something
 1      Region    something

客户列：

ListID Name Address City State Zip Phone

我希望得到结果

Name Address City State Zip Phone Type Region

Answer 1

SELECT customers.*, data_type.DataValue AS Type, data_region.DataValue AS Region
FROM   customers
  JOIN cust_data AS data_type ON (
         data_type.ListID   = customers.List_ID
     AND data_type.DataName = 'Type'
  )
  JOIN cust_data AS data_region ON (
         data_region.ListID   = customers.List_ID
     AND data_region.DataName = 'Region'
  )

Answer 2

您可以使用群组查询来执行此操作。您可以按ListID分组以获得单行这一事实使得这相对简单 - 只需有条件地选择并根据需要对 DataValue 字段进行别名：

SELECT c.Name, c.Address, c.City, c.State, c.Zip, c.Phone,
    MAX (CASE WHEN d.DataName = 'type' THEN DataValue ELSE NULL END) AS  `Type`,
    MAX (CASE WHEN d.DataName = 'Region' THEN DataValue ELSE NULL END) AS  `Region`
FROM customers c, cust_data d
WHERE c.ListID = d.ListID
GROUP BY c.ListID, c.Name, c.Address, c.City, c.State, c.Zip, c.Phone

我试图从行到匹配到定义列中的数据

2 个答案: