创建外键约束时出现问题：MySQL

Question

类别表

CREATE TABLE IF NOT EXISTS `tblcategory` (
  `CategoryID` int(11) NOT NULL AUTO_INCREMENT,
  `Category` varchar(25) NOT NULL,
  `IsActive` tinyint(1) NOT NULL,
  PRIMARY KEY (`CategoryID`),
  UNIQUE KEY `UK_tblcategory_Category` (`Category`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=6 ;

子类别表

CREATE TABLE IF NOT EXISTS `tblsubcategory` (
  `SubCategoryID` int(11) NOT NULL AUTO_INCREMENT,
  `SubCategory` varchar(25) NOT NULL,
  `CategoryID` int(11) NOT NULL,
  `IsActive` int(11) NOT NULL,
  PRIMARY KEY (`SubCategoryID`),
  UNIQUE KEY `UK_tblSubCategory_SubCategory_CategoryID` (`CategoryID`,`SubCategory`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;

以下是我试图在子Catgory表中添加外键引用的查询

ALTER TABLE tblsubcategory
ADD CONSTRAINT FK_tblsubcategory_tblcategory_CategoryID
FOREIGN KEY (CategoryID)
REFERENCES tblsubcategory(CategoryID)

MySQL说

  

1005 - 无法创建表myapp。#sql-6b8_33（错误：150“外键约束形成错误”）

问题

我错过了什么吗？

Answer 1

我认为您打算在其他表格中引用CategoryID ...

ALTER TABLE tblsubcategory
ADD CONSTRAINT FK_tblsubcategory_tblcategory_CategoryID
FOREIGN KEY (CategoryID)
REFERENCES tblcategory(CategoryID)

Answer 2

您需要引用Category表，而不是SubCategory表：

ALTER TABLE tblsubcategory
ADD CONSTRAINT FK_tblsubcategory_tblcategory_CategoryID
FOREIGN KEY (CategoryID)
REFERENCES tblcategory(CategoryID)
           ^^^^^^^^^^^