獲取不符合條件的行數

Question

給定一個帶有客戶和產品的簡單表格（訂單明細/歷史記錄）：

+--------------------+
| customer | product |
+--------------------+
| Smith    | p1      |
| Smith    | p3      |
| Jones    | p1      |
| Jones    | p2      |
| Davis    | p3      |
| Davis    | p9      |
| Brown    | p1      |
| Brown    | p2      | 
| Brown    | p5      |
+----------+---------+

我想在上述數據集中列出從未訂購產品p1的所有客戶，即Davis 。

這是我開始的地方，但是，它當然行不通，我無法想到下一步要去哪里：

select 
    customer,
    count(*) as c 
where product='p1' 
    and c = 0

Answer 1

試試看：

select customer
from MyTable
where customer not in (select customer from MyTable where Product = 'P1')

Answer 2

這是使用聚合查詢的一種方法：

select customer
from t
group by customer
having sum(case when product = 'p1' then 1 else 0 end) = 0

這為您提供了表中的所有客戶。 如果您有單獨的客戶列表，則可以使用：

select customer
from customerTable
where customer not in (select customer from t where product = 'p1')

Answer 3

您也可以使用這種方法

 SELECT t.CustomerName
 FROM Table t
 WHERE NOT EXISTS (SELECT 1 
                   FROM Table t2 
                   WHERE t2.CustomerName = t.CustomerName
                   AND t2.ProductName = 'p1')