内同一列加入

Customer Table 
---------------------- 
CustomerName 
Peter 
Sam 


Sales Table 
----------------------- 
ProductName Customer 
Cloth   Peter 
Mobile   Peter 
Cloth   Sam 
Laptop   Sam

预期结果内同一列加入

Customer 
Sam

我想导致的客户谁buyed“布”，但不是“移动”，我想

select c.CustomerName from Customer c inner join Sales s1 on (s1.customer = c.customername and s1.productname = 'Cloth') inner join Sales s2 on (s2.customer = c.customername and s2.productname != 'Mobile');

但它总是返回两个条目

Customer 
Peter 
Sam 
Sam

来源

2013-05-10 BreakHead

试试这个：

select c.CustomerName 
from Customer c 
where exists(select 1 from sales s1 where s1.customer = c.customername and s1.productname = 'Cloth') 
and not exists (select 1 from sales s2 where s2.customer = c.customername and s2.productname = 'Mobile')

来源

2013-05-10 12:53:48

相关的子查询会更好，因为您对购买多次布料的客户不感兴趣。

select 
    c.CustomerName 
from 
    Customer c 
where 
    exists (
    select null 
    from sales 
    where sales.customer = c.customername and 
      s1.productname = 'Cloth') and 
    not exists (
    select null 
    from sales 
    where sales.customer = c.customername and 
      s1.productname = 'Mobile');

来源

2013-05-10 12:54:36

谢谢@David是不可能与innerjoins？ – BreakHead 2013-05-10 12:59:32

您必须将外部联接销售给“移动”才能找到销售，然后从结果中除去找到记录的结果以及“布料”的内部联接，然后删除结果集。它根本不会有效。 – 2013-05-10 13:03:52

您可以使用Oracle MINUS运算符来简化它;

SELECT "Customer" FROM SalesTable WHERE "ProductName"='Cloth' 
MINUS 
SELECT "Customer" FROM SalesTable WHERE "ProductName"='Mobile'

另一个稍微复杂的选项是LEFT JOIN;

SELECT DISTINCT s1."Customer" 
FROM SalesTable s1 
LEFT JOIN SalesTable s2 
ON s1."Customer" = s2."Customer" 
    AND s2."ProductName" = 'Mobile' 
WHERE s1."ProductName" = 'Cloth' 
    AND s2."Customer" IS NULL;

An SQLfiddle to test both with。

来源

2013-05-10 12:58:33

首先你应该检查你的数据库模式。
如果没有ID，你永远不会做内部连接。尝试使用关系创建表格。就像这样：

create table customer 
(
id_customer  int not null, 
ds_customername varchar(80) null, 
primary key (id_customer) 
) 

create table products 
(
id_product int not null, 
ds_product varchar(100) null, 
primary key (id_product) 
) 

create table sales 
(
id_sales int not null, 
id_product int not null, 
id_customer int not null, 
foreign key (id_product) references products (id_product), 
foreign key (id_customer) references customer (id_customer) 
) 

select customer.ds_customername 
from customer 
     inner join sales (customer.id_customer = sales.id_customer) 
     inner join products (products.id_product = sales.id_product) 
where products.ds_product = 'Cloth'

好吧，如果你不能做到这一点，你可以做你的查询（以旧的方式）是：

select Customer.customername 
    from  Customer 
      inner join on (customer.customername = sales.customer) 
    where sales.productname = 'Cloth'

我希望帮你。拥抱， Vin。

来源

2013-05-10 13:07:42

这是“set-set-set”查询的示例。我认为一个好的方法是使用聚合：

select s.Customer 
from Sales s 
group by s.Customer 
having sum(case when s.ProductName = 'Cloth' then 1 else 0 end) > 0 and -- has cloth 
     sum(case when s.ProductName = 'Mobile' then 1 else 0 end) = 0  -- does not have mobile

我更喜欢把逻辑having子句中，因为它是非常灵活。您可以很容易地为其他产品添加附加条件。

来源

2013-05-10 13:14:55

内同一列加入

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