Question

基本上我们说我有一个＆＃34; Business＆＃34;拥有它服务的邮政编码。我们还假设我有另一个设置费用的关系表。

CREATE TABLE [dbo].[BusinessPostalCodes] 
(
    [BusinessPostalCodeId]         INT           IDENTITY (1, 1) NOT NULL,
    [BusinessId]                   INT           NOT NULL,
    [PostalCode]                    VARCHAR (10)  NOT NULL
)

CREATE TABLE [dbo].[BusinessPostalCodeFees]
(
    [BusinessId] INT NOT NULL, 
    [BusinessProfileFeeTypeId] INT NOT NULL,
    [BusinessPostalCodeId] INT NOT NULL, 
    [Fee] SMALLMONEY NULL
)

我想知道是否可以在BusinessPostalCodeFees上设置外键（或其他内容），以确保BusinessId的{{1}}与BusinessPostalCodes相同BusinessId的{{1}}。

我意识到我可以完全删除BusinessPostalCodeFees，但我更愿意保留这个专栏并保证它们是相同的。我有什么可以做的吗？

Answer 1

听起来（如果我错了，请纠正我）您正在尝试确保BusinessPostalCodeFees的BusinessId和BusinessPostalCodeId列中的任何条目都与BusinessPostalCodes表中的条目匹配。如果是这样，那么是的，你可以definitely have a foreign key that references a compound primary key。

但是，如果您需要保留BusinessId，我建议您将表格比标准化步骤更进一步。你最终会得到重复的数据。

另外，我建议您不要在SQL中使用货币数据类型：See here.

Answer 2

最后，Jeffrey的解决方案对我的特殊情况并不适用。关系中的两列必须是唯一的（如复合键）。原来答案（对我而言）是 Checked Constraint 。

创建一个您希望约束通过或失败的函数：

CREATE FUNCTION [dbo].[MatchingBusinessIdPostalCodeAndProfileFeeType]
(
    @BusinessId int,
    @BusinessPostalCodeId int,
    @BusinessProfileFeeTypeId int
)
RETURNS BIT
AS
BEGIN

    -- This works because BusinessPostalCodeId is a unique Id.
    -- If businessId doesn't match, its filtered out.   
    DECLARE @pcCount AS INT 
    SET @pcCount = (SELECT COUNT(*) 
        FROM BusinessPostalCodes 
        WHERE BusinessPostalCodeId = @BusinessPostalCodeId AND 
            BusinessId = @BusinessId)


    -- This works because BusinessProfileFeeTypeId is a unique Id.
    -- If businessId doesn't match, its filtered out.   
    DECLARE @ftCount AS INT 
    SET @ftCount = (SELECT COUNT(*) 
        FROM BusinessProfileFeeTypes
        WHERE BusinessProfileFeeTypeId = @BusinessProfileFeeTypeId AND 
            BusinessId = @BusinessId)

    -- Both should have only one record
    BEGIN IF (@pcCount = 1 AND @ftCount = 1)
        RETURN 1
    END

    RETURN 0
END

然后将其添加到您的表格中：

CONSTRAINT [CK_BusinessPostalCodeFees_MatchingBusinessIdPostalCodeAndProfileFeeType] 
CHECK (dbo.MatchingBusinessIdPostalCodeAndProfileFeeType(
    BusinessId, 
    BusinessPostalCodeId, 
    BusinessProfileFeeTypeId) = 1)

确保外键的外键与基本外键匹配

2 个答案: