Mysql Error can't add foreign key constraint when importing sql document

Question

When I was importing a Sql document, I got an error "can't add foreign key constraint". It seems that I can't use the foreign key 'cid' in the table 'book'. And the data type for the child column matches the parent column. I can't figure it out.

CREATE TABLE `book` (
  `bid` char(32) NOT NULL,
  `bname` varchar(100) DEFAULT NULL,
  `price` decimal(10,2) DEFAULT NULL,
  `author` varchar(50) DEFAULT NULL,
  `image` varchar(200) DEFAULT NULL,
  `cid` char(32) DEFAULT NULL,
  `isdel` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`bid`),
  KEY `cid` (`cid`),
  CONSTRAINT `book_ibfk_1` FOREIGN KEY (`cid`) REFERENCES `category` (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `category` (
  `cid` char(32) NOT NULL,
  `cname` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

When you create the book table first, it tries to create references for the table category(which was not created yet), try creating the category table first,

CREATE TABLE `category` (
  `cid` char(32) NOT NULL,
  `cname` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `book` (
  `bid` char(32) NOT NULL,
  `bname` varchar(100) DEFAULT NULL,
  `price` decimal(10,2) DEFAULT NULL,
  `author` varchar(50) DEFAULT NULL,
  `image` varchar(200) DEFAULT NULL,
  `cid` char(32) DEFAULT NULL,
  `isdel` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`bid`),
  KEY `cid` (`cid`),
  CONSTRAINT `book_ibfk_1` FOREIGN KEY (`cid`) REFERENCES `category` (`cid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

I did it on SQL fiddle and worked fine.