Question

在我的数据库中，我有3个关于不同类型资产的表： house 和地面，定位建筑物和股票。

另一张表是关于借用。

现在我必须链接资产和借用。规则是： - 一个借款只能与一个资产挂钩。 - 一项资产可以选择性地与一项或多项借款挂钩。

我从这个数据库设计开始：

CREATE TABLE CUSTOMER
(
  CUSTOMER_ID INT NOT NULL,
  [...] 

  CONSTRAINT PK_CUS_ID PRIMARY KEY (CUS_ID)
)

CREATE TABLE ASSET1
(
  ASSET1_ID   INT NOT NULL,
  CUSTOMER_ID INT NOT NULL,
  [...]

  CONSTRAINT PK_ASSET1_ID PRIMARY KEY (ASSET1_ID),  
  CONSTRAINT FK_ASSET1_CUSTOMER FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMER (CUSTOMER_ID) ON DELETE NO ACTION ON UPDATE NO ACTION
)

CREATE TABLE ASSET2
(
  ASSET2_ID   INT NOT NULL,
  CUSTOMER_ID INT NOT NULL,
  [...]

  CONSTRAINT PK_ASSET2_ID PRIMARY KEY (ASSET2_ID),  
  CONSTRAINT FK_ASSET2_CUSTOMER FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMER (CUSTOMER_ID) ON DELETE NO ACTION ON UPDATE NO ACTION
)

CREATE TABLE ASSET3
(
  ASSET3_ID   INT NOT NULL,
  CUSTOMER_ID INT NOT NULL,
  [...]

  CONSTRAINT PK_ASSET3_ID PRIMARY KEY (ASSET3_ID),  
  CONSTRAINT FK_ASSET3_CUSTOMER FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMER (CUSTOMER_ID) ON DELETE NO ACTION ON UPDATE NO ACTION
)

CREATE TABLE BORROWING
(
  BORROWING_ID INT NOT NULL,
  CUSTOMER_ID  INT NOT NULL,
  ASSET1_ID    INT     NULL,
  ASSET2_ID    INT     NULL,
  ASSET3_ID    INT     NULL,
  [...]

  CONSTRAINT PK_BORROWING_ID PRIMARY KEY (BORROWING_ID),

  CONSTRAINT FK_BORROWING_CUSTOMER FOREIGN KEY (CUSTOMER_ID) REFERENCES CUSTOMER (CUSTOMER_ID) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT FK_BORROWING_ASSET1   FOREIGN KEY (ASSET1_ID  ) REFERENCES ASSET1   (ASSET1_ID  ) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT FK_BORROWING_ASSET2   FOREIGN KEY (ASSET2_ID  ) REFERENCES ASSET2   (ASSET2_ID  ) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT FK_BORROWING_ASSET3   FOREIGN KEY (ASSET3_ID  ) REFERENCES ASSET3   (ASSET3_ID  ) ON DELETE NO ACTION ON UPDATE NO ACTION,

  CONSTRAINT CHK_BORROWING CHECK 
  (
      ((ASSET1_ID IS     NULL) AND (ASSET2_ID IS     NULL) AND (ASSET3_ID IS     NULL))
   OR ((ASSET1_ID IS NOT NULL) AND (ASSET2_ID IS     NULL) AND (ASSET3_ID IS     NULL))
   OR ((ASSET1_ID IS     NULL) AND (ASSET2_ID IS NOT NULL) AND (ASSET3_ID IS     NULL))
   OR ((ASSET1_ID IS     NULL) AND (ASSET2_ID IS     NULL) AND (ASSET3_ID IS NOT NULL))
  )
)

它的工作和参照完整性似乎没问题。

但是我已经知道将来我必须在我的数据库中添加更多资源，CHK_BORROWING将变成怪物。

我的问题：是否有更好，更清洁，更简单的解决方案？

谢谢

Answer 1

根据Walter Mitty的建议，解决方案是Class Table Inheritance。

如果您使用了Class Table继承，则可以创建一个表，让我们来称之为ASSETS_GENERIC。每种资产，无论何种类型，都会有在此表中输入。现在你可以在两者之间建立一个有限的联系以通常的方式借用和Assets_generic（参考文献）。现在你在ASSETS_GENERIC和每个ASSETx之间建立联系表。

数据库设计：借贷资产融资

1 个答案: