Question

我正在做家庭作业。我必须为视频商店建立一个数据库。以下所有工作：

CREATE TABLE Stock
(
PKStock_ID VARCHAR(8) NOT NULL,
FKTitle VARCHAR(8) NOT NULL,
NoOfDVD INT(10) NOT NULL,
NoOfVHS INT(10) NOT NULL,
PRIMARY KEY (PKStock_ID)
);

CREATE TABLE Inventory
(
PKUnique_ID VARCHAR(8) NOT NULL,
DistributorSerialNo VARCHAR(8) NOT NULL,
Distributor_ID VARCHAR(8) NOT NULL,
FKTitle_ID VARCHAR(8) NOT NULL,
InStock CHAR(1) NOT NULL, 
DateOut TIMESTAMP,
DateBack TIMESTAMP,
Customer_ID VARCHAR(8) NOT NULL,
Rental_Price DECIMAL(4,2) NOT NULL,
PRIMARY KEY (PKUnique_ID)
);

CREATE TABLE Movie
(
PKTitle_ID VARCHAR(8) NOT NULL,
FKTitle_ID VARCHAR(8) NOT NULL,
Title VARCHAR(30),
Genre VARCHAR(8),
YearReleased INT,
Length INT,
PRIMARY KEY (PKTitle_ID)
);

CREATE TABLE Actors
(
PKActor_ID VARCHAR(8) NOT NULL,
FKActor_ID VARCHAR(8) NOT NULL, 
Actors VARCHAR(30),
PRIMARY KEY (PKActor_ID)
);

CREATE TABLE Awards
(
PKAward_ID VARCHAR(8) NOT NULL,
FKAward_ID VARCHAR(8) NOT NULL,
Awards VARCHAR(30),
PRIMARY KEY (PKAward_ID)
);

CREATE TABLE Directors
(
PKDirector_ID VARCHAR(8) NOT NULL,
FKDirector_ID VARCHAR(8) NOT NULL,
Directors VARCHAR(30),
PRIMARY KEY (PKDirector_ID)
);

CREATE TABLE ElectronicCatalogue
(
PKElectronicCatalogue VARCHAR(8) NOT NULL,
FKDistributor_ID VARCHAR(8) NOT NULL,
DistributorSerialNo VARCHAR(8) NOT NULL,
Price DECIMAL(6,2) NOT NULL,
PRIMARY KEY (PKElectronicCatalogue)
);

CREATE TABLE Distributors
(
PKDistributor_ID VARCHAR(8) NOT NULL,
FKDistributor_ID VARCHAR(8) NOT NULL,
NameOfDistributer VARCHAR(30) NOT NULL,
Horror CHAR(1) NOT NULL, 
Drama CHAR(1) NOT NULL, 
Comedy CHAR(1) NOT NULL, 
Action CHAR(1) NOT NULL, 
Thrillers CHAR(1) NOT NULL,
PRIMARY KEY (PKDistributor_ID)
);

CREATE TABLE Customers
(
PKCustomer_ID VARCHAR(8) NOT NULL,
FKUnique_ID VARCHAR(8) NOT NULL,
Name VARCHAR(30),
Address VARCHAR(100),
Phone INT NOT NULL,
PRIMARY KEY (PKCustomer_ID)
);

CREATE TABLE Fees
(
PKFee_ID VARCHAR(8) NOT NULL,
FK_ID VARCHAR(8) NOT NULL,
Damages DECIMAL(10,2) NOT NULL,
Late DECIMAL(10,2) NOT NULL,
PRIMARY KEY (PKFee_ID)
);

ALTER TABLE Stock
ADD FOREIGN KEY (FKTitle)
REFERENCES Inventory(PKUnique_ID);

ALTER TABLE Movie
ADD FOREIGN KEY (FKTitle_ID)
REFERENCES Stock (PKStock_ID);

ALTER TABLE Actors
ADD FOREIGN KEY (FKActor_ID)
REFERENCES Movie (PKTitle_ID);

ALTER TABLE Awards
ADD FOREIGN KEY (FKAward_ID)
REFERENCES Movie (PKTitle_ID);

ALTER TABLE Directors
ADD FOREIGN KEY (FKDirector_ID)
REFERENCES Movie (PKTitle_ID);

ALTER TABLE ElectronicCatalogue
ADD FOREIGN KEY (FKDistributor_ID)
REFERENCES Inventory (PKUnique_ID);

ALTER TABLE Distributors
ADD FOREIGN KEY (FKDistributor_ID)
REFERENCES ElectronicCatalogue (PKElectronicCatalogue);

我接下来想要将Inventory表连接到customers表。当我执行以下操作时：

ALTER TABLE Customers
ADD FOREIGN KEY (FKUnique_ID)
REFERENCES Inventory (Customer_ID);

我收到此错误：

#1005 - Can't create table 'mm.#sql-9f69_110' (errno: 150)

我做错了什么？

Answer 1

外键应指向唯一列（主键或唯一）。您的Inventory (Customer_ID)并非唯一。

我认为你正在努力：

ALTER TABLE Inventory
ADD CONSTRAINT fk1_Inv FOREIGN KEY (Customer_ID)
REFERENCES Customers (PKCustomer_ID);

Answer 2

不确定为什么你没有得到完整的消息，但是有一个与MySQL捆绑在一起的命令行工具，它提供了有关这样的神秘错误消息的更多信息（或者你只能通过Google获取错误代码）：

C:>perror 150
MySQL error code 150: Foreign key constraint is incorrectly formed

如果您拥有SUPER权限，则可以通过此查询获取更多详细信息：

show engine innodb status

在这种情况下，您会看到：

LATEST FOREIGN KEY ERROR
------------------------
130226 21:00:25 Error in foreign key constraint of table test/#sql-1d98_1:
FOREIGN KEY (FKUnique_ID)
REFERENCES Inventory (Customer_ID):
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.
Note that the internal storage type of ENUM and SET changed in
tables created with >= InnoDB-4.1.12, and such columns in old tables
cannot be referenced by such columns in new tables.
See http://dev.mysql.com/doc/refman/5.0/en/innodb-foreign-key-constraints.html
for correct foreign key definition.

所以你错过了解释的索引。

编辑：正如其他答案所指出的那样，如果没有索引，那是因为您链接到了错误的列。

Answer 3

正如ÁlvaroG。Vicario所说你缺少一个索引，这是因为你没有正确使用外键。

ALTER TABLE Customers
ADD FOREIGN KEY (FKUnique_ID)
REFERENCES Inventory (Customer_ID);

这应该是：

ALTER TABLE Inventory
ADD FOREIGN KEY (Customer_ID)
REFERENCES Customer(PKCustomer_ID);

外键检查Inventory表中的客户是否实际存在于Customers表中。因此，Inventory这里是您要添加外键的表，它在Customer表的主键中引用。

您要做的是引用Inventory中的Customer_ID，它只是一个VARCHAR（8）列，而不是主键（索引）。

你也应该仔细检查你的其他改变陈述。

Answer 4

事实证明，这些表之间有不同的排序规则设置。在我的例子中，我们有latin_swedish_ci和utf8_general_ci

＃1005 - 通过FOREIGN KEY连接表时，无法在ALTER TABLE上创建表

4 个答案: