选择仅与另一个表中的记录关联的记录

Question

不确定标题是否完整地解释了这个场景，所以我会尽可能描述。我使用的是 SQL Server 数据库，有以下 4 个表：

客户：

CustomerID   CustomerName
--------------------------
100001       Mr J Bloggs
100002       Mr J Smith

政策：

PolicyID  PolicyTypeID  CustomerID
-----------------------------------
100001    100001        100001
100002    100002        100001
100003    100003        100001
100004    100001        100002
100005    100002        100002

政策类型：

PolicyTypeID   PolTypeName   ProviderID
-----------------------------------------
100001         ISA           100001
100002         Pension       100001
100003         ISA           100002

供应商：

ProviderID    ProviderName
--------------------------
100001        ABC Ltd
100002        Bloggs Plc

这显然是一个精简的版本，实际的数据库包含更多的记录。我要做的是返回仅拥有来自某个提供商的产品的客户列表。所以在上面的例子中，如果我想用这个 SQL 返回与 ABC Ltd 有政策的客户：

SELECT 
    C.CustomerName, P.PolicyID, PT.PolTypeName, Providers.ProviderName
FROM 
    Customers C 
LEFT JOIN 
    Policies P ON C.CustomerID = P.CustomerID
LEFT JOIN 
    PolicyTypes PT ON P.PolicyTypeID = PT.PolicyTypeID
LEFT JOIN 
    Providers PR ON PR.ProviderID = PT.ProviderID
WHERE 
    PR.ProviderID = 100001

它当前将返回客户表中的两个客户。但客户 Mr J Bloggs 实际上也持有 Bloggs Plc 提供的政策。我不想要这个。我只想退回只持有 ABC Ltd 保单的客户，所以我需要的 SQL 应该只退回 Mr J Smith。

希望我已经说清楚了，如果没有请告诉我。

在此先感谢

史蒂夫

Answer 1

脏但可读：

SELECT C.CustomerName, P.PolicyID, PT.PolTypeName, Providers.ProviderName
FROM Customers C LEFT JOIN Policies P ON C.CustomerID = P.CustomerID
LEFT JOIN PolicyTypes PT ON P.PolicyTypeID = PT.PolicyTypeID
LEFT JOIN Providers PR ON PR.ProviderID = PT.ProviderID
WHERE PR.ProviderID = 100001 AND C.CustomerName NOT IN (
    SELECT C.CustomerName
    FROM Customers C LEFT JOIN Policies P ON C.CustomerID = P.CustomerID
    LEFT JOIN PolicyTypes PT ON P.PolicyTypeID = PT.PolicyTypeID
    LEFT JOIN Providers PR ON PR.ProviderID = PT.ProviderID
    WHERE PR.ProviderID <> 100001
)

Answer 2

这个想法是您另外对链接到其他提供商的 customerid 执行 NOT IN：

SELECT C.CustomerName, P.PolicyID, PT.PolTypeName, Providers.ProviderName
FROM Customers C LEFT JOIN Policies P ON C.CustomerID = P.CustomerID
LEFT JOIN PolicyTypes PT ON P.PolicyTypeID = PT.PolicyTypeID
LEFT JOIN Providers PR ON PR.ProviderID = PT.ProviderID
WHERE PR.ProviderID = 100001
--NEW PART
AND C.CustomerID NOT IN
(
    SELECT P.CustomerID
    FROM Policies P
    LEFT JOIN PolicyTypes PT ON P.PolicyTypeID = PT.PolicyTypeID
    LEFT JOIN Providers PR ON PR.ProviderID = PT.ProviderID
    WHERE PR.ProviderID <> 100001
)

Answer 3

试试这个...

SELECT C.CustomerName, P.PolicyID, PT.PolTypeName, Providers.ProviderName 
    from Customers C inner join POLICIES P ON C.CustomerID = P.CustomerID
    inner join PT ON P.PolicyTypeID = PT.PolicyTypeID
    inner join Providers PR ON PR.ProviderID = PT.ProviderID
    where  PR.ProviderID = 100001 and c.CustomerID not in 
    (SELECT C.CustomerID from Customers C 
    inner join POLICIES P ON C.CustomerID = P.CustomerID 
    inner join PT ON P.PolicyTypeID = PT.PolicyTypeID 
    inner join Providers PR ON PR.ProviderID = PT.ProviderID where  PR.ProviderID <> 100001)