Question

之前有一个问题，这个代码已经解决并导致表工作但现在我收到错误1005并且由于fk而无法创建表

这是第一个表的代码

SET FOREIGN_KEY_CHECKS = 0;
DROP TABLE IF EXISTS Customer;
CREATE TABLE Customer
(
CustomerNumber int NOT NULL,
CustomerName varchar(255),
CustomerAddress varchar(255),
CustomerPhoneNumber varchar(255),
JoinDate varchar(255),
PetName varchar(255),
PayScheme varchar(255),
PremiumPayDate varchar(255),
PRIMARY KEY (CustomerNumber)
);

这是第二个表的代码

DROP TABLE IF EXISTS Policies;    
CREATE TABLE Policies
(
PolicyID int NOT NULL,
PolicyNumber int NOT NULL,
PetType varchar(255),
CustomerNumber int NOT NULL, 
PetName varchar(255),
EffectiveDate varchar(255),
PRIMARY KEY (PolicyID),
    CONSTRAINT fk_CustomerNumber
    FOREIGN KEY (CustomerNumber)
    REFERENCES Customer(CustomerNumber),
    CONSTRAINT fk_PetName
    FOREIGN KEY (PetName)
    REFERENCES Customer(PetName)
    );

错误代码

      19:05:38CREATE TABLE Policies (     PolicyID int NOT NULL,     PolicyNumber int NOT NULL,     PetType varchar(255),     CustomerNumber int NOT NULL,      PetName varchar(255),     EffectiveDate varchar(255),     PRIMARY KEY (PolicyID),         CONSTRAINT fk_CustomerNumber FOREIGN KEY (CustomerNumber) REFERENCES Customer(CustomerNumber),  CONSTRAINT fk_PetName     FOREIGN KEY (PetName)     REFERENCES Customer(PetName) )    Error Code: 1005. Can't create table 'cis22723684.Policies' (errno: 150)    0.031 sec

我已经解决了问题，请参阅代码编辑。

  SET FOREIGN_KEY_CHECKS = 0;
  DROP TABLE IF EXISTS Customer;
  CREATE TABLE Customer
  (
     CustomerNumber int NOT NULL,
     CustomerName varchar(255),
     CustomerAddress varchar(255),
     CustomerPhoneNumber varchar(255),
     JoinDate varchar(255),
     PetName varchar(255),
     PayScheme varchar(255),
     PremiumPayDate varchar(255),
     PRIMARY KEY (CustomerNumber, PetName)
     );

     DROP TABLE IF EXISTS Policies;    
     CREATE TABLE Policies
     (
     PolicyID int NOT NULL,
     PolicyNumber int NOT NULL,
     PetType varchar(255),
     CustomerNumber int NOT NULL, 
     PetName varchar(255),
     EffectiveDate varchar(255),
     PRIMARY KEY (PolicyID),
     CONSTRAINT fk_CustomerNumber
     FOREIGN KEY (CustomerNumber, PetName)
     REFERENCES Customer(CustomerNumber, PetName)
     );

它似乎使用pk作为复合并在一个约束下包含pks

然而，当我尝试创建一个新的fk时，尽管保留了使用的代码，我仍然收到与之前相同的错误代码

第一张表

  SET FOREIGN_KEY_CHECKS = 0;
  DROP TABLE IF EXISTS Customer;
  CREATE TABLE Customer
  (
    CustomerNumber int NOT NULL,
    CustomerName varchar(255),
    CustomerAddress varchar(255),
    CustomerPhoneNumber varchar(255),
    JoinDate varchar(255),
    PetName varchar(255),
    PayScheme varchar(255),
    PremiumPayDate varchar(255),
    PRIMARY KEY (CustomerNumber, PetName)
    );

第二张表

  DROP TABLE IF EXISTS Policies;    
  CREATE TABLE Policies
  (
   PolicyID int NOT NULL,
   PolicyNumber int NOT NULL,
   PetType varchar(255),
   CustomerNumber int NOT NULL, 
   PetName varchar(255),
   EffectiveDate varchar(255),
   PRIMARY KEY (PolicyID), 
      CONSTRAINT fk_CustomerNumber_PetName
      FOREIGN KEY (CustomerNumber, PetName)
      REFERENCES Customer(CustomerNumber, PetName)
   );

第三表

  DROP TABLE IF EXISTS Claims;    
  CREATE TABLE Claims
  (
   ClaimsID int NOT NULL,
   AmountForReimbursement varchar(255),
   PolicyID varchar(255),
       PRIMARY KEY (ClaimsID),
       CONSTRAINT fk_PolicyID
       FOREIGN KEY (PolicyID)
       REFERENCES Policies(PolicyID)      
   );

是一个简单的问题，int NOT NULL被识别为varchar，我需要一些睡眠：'）

Answer 1

问题出现在下面的第二个约束中，您尝试引用非键列PetName这是不可能的，而且它违反了规范化概念。您的Customer表仅将主键定义为PRIMARY KEY (CustomerNumber)。

CONSTRAINT fk_PetName
FOREIGN KEY (PetName)
REFERENCES Customer(PetName)

从CREATE语句中删除上面提到的FK约束定义，它可以正常工作。不要相信，然后看到这个小提琴：http://sqlfiddle.com/#!9/86a927

根据您的编辑：您的FK约束定义必须如下所示。请参阅修改过的小提琴：http://sqlfiddle.com/#!9/3a019

CONSTRAINT fk_CustomerNumber_PetName
FOREIGN KEY (CustomerNumber, PetName)
REFERENCES Customer(CustomerNumber, PetName)

MySQL外键导致表丢失

1 个答案: