Question

好的，我有2张桌子。一个Product List表和一个Orders表。我的Table1中会有几个相同的ProductID，因为每个ProductID都有几个部分（IE：第7部分）。

PartNumber将是一个数字。如何设计查询以找到购买其中一个零件号的所有客户，但不是所有购买单个产品ID的零件号？

我只是学习MySQL的基础知识，所以任何帮助都会非常感激！

表1 - 产品清单

UniqueIDKey
Product ID
PartNumber

表2 - 订单

UniqueIDKey
Product ID Ordered
PartNumber Ordered
Customer ID

所以订单可能如下所示：

UniqueIDKey: 77
Product ID Ordered: 1001
PartNumber Ordered: 3
Customer ID: 2000001

而且，Table1 - Product List的几行可能如下所示：

UniqueIDKey     Product ID     PartNumber
77              1001           1
78              1001           2
79              1001           3

Answer 1

您需要先了解每种产品下的部件总数了解哪些客户购买了产品的某些部分而不是整体。
表别名B附带的查询提供了部分计数每个产品。
表别名A附带的查询为每个查询提供了条件 <customer,product>配对已购买零件的总数。
现在剩下的就是匹配购买部件的总数是多少少于产品的总数。

在这种方法中，查询如下所示：

SELECT 
 A.customer_id,
 A.product_id,
 A.total_parts_of_product_customer_purchased AS total_purchased,
 B.total_parts,
 B.total_parts - A.total_parts_of_product_customer_purchased AS didnot_purchase
FROM (
  SELECT 
    customer_id,
    product_id,
    count(part_number) AS total_parts_of_product_customer_purchased 
  FROM Orders AS ordr 
  GROUP BY 
      customer_id, product_id
) AS A 
INNER JOIN (
   SELECT 
    product_id,
    count(part_number) AS total_parts
   FROM product_list AS pl 
   GROUP BY product_id
) AS B 
ON A.product_id = B.product_id
WHERE A.total_parts_of_product_customer_purchased < B.total_parts
ORDER BY A.customer_id;

Answer 2

使用VeryLargeBlackBoxMethod()获取客户，product_id和part_numbers的所有组合。 [STAThread] public static void Main() { var testTimer = new System.Threading.Timer((s) => { Console.WriteLine("This code never run"); }); testTimer.Change(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1)); PrintAvailableThreads(); // ThreadPool can`t provide a new Task after this method executing VeryLargeBlackBoxMethod(); PrintAvailableThreads(); Task.Factory.StartNew(() => { Console.WriteLine("This code never run too"); }); ThreadPool.QueueUserWorkItem((p) => { Console.WriteLine("And this code newer run"); }); var thread = new Thread(() => { Console.WriteLine("But this code work"); }); thread.Start(); Console.ReadLine(); } private static void PrintAvailableThreads() { var work = 0; var completionThreads = 0; ThreadPool.GetAvailableThreads(out work, out completionThreads); Console.WriteLine("worker threads {0}, completionThreads {1}", work, completionThreads); } // Console output: // worker threads 32767, completionThreads 1000 // worker threads 32762, completionThreads 1000 // But this code work订购了此结果表，以便客户无法订购产品中的所有零件。

cross join

MySQL查询 - 获取尚未购买单个产品ID的所有部分的客户

2 个答案: