Question

我一直在阅读如何解决这个问题，但由于我缺乏正确构建此查询或甚至搜索正确答案的知识，我将不得不在这里询问并希望您可以帮助我。

假设我有一个名为VENDORS的表格如下：

ID|name   |phone   |phone_type
 1| Andy  |305332  |office   
 1| Andy  |999999  |fax    
 1| Andy  |555555  |cellphone       
 2| Jack  |222222  |office       
 2| Jack  |444444  |fax     
 3| Peter |234234  |office       
 3| Peter |434345  |cellphone

如何构建查询以便我得到：

ID|name   |phone   |fax      |cellphone
 1| Andy  |305332  |999999   |555555
 2| Jack  |222222  |444444   |NULL       
 3| Peter |234234  |NULL     |434345

我在想这样的事情：

SELECT 
    id,
    name, 
    CASE 
        WHEN phone_type = 'office' 
            THEN phone END AS phone
        WHEN phone_type = 'fax' 
            THEN phone END AS fax,
        WHEN phone_type = 'cellphone' 
            THEN phone END AS cellphone  
FROM `VENDORS`
GROUP BY id

但当然这不起作用，不知道如何得到我想要的东西，这似乎很容易，但我完全迷失了。

Answer 1

尝试

SELECT 
    id,
    name, 
    CASE WHEN phone_type = 'office' 
            THEN phone 
            ELSE NULL END AS office,
    CASE WHEN phone_type = 'fax' 
            THEN phone 
            ELSE NULL END AS fax,
    CASE WHEN phone_type = 'cellphone' 
            THEN phone 
            ELSE NULL END AS cellphone  
FROM `VENDORS`
GROUP BY name

Answer 2

这是一个带子查询的工作解决方案：

SELECT id, name,
    (SELECT phone FROM vendors WHERE id = v.id AND phone_type = 'office') as office,
    (SELECT phone FROM vendors WHERE id = v.id AND phone_type = 'fax') as fax,
    (SELECT phone FROM vendors WHERE id = v.id AND phone_type = 'cellphone') as cellphone
FROM vendors v 
GROUP BY id

你可以在这里找到一个工作小提琴： http://sqlfiddle.com/#!9/42b355/2

有条件地在一系列部分重复的行上选择列和组结果

2 个答案: