MySQL MariaDB不会使用外键创建Table

Question

I'm having a problem with my SQL Tables. So I have my Usertable:

CREATE TABLE IF NOT EXISTS `user` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `NICKNAME` varchar(50) NOT NULL,
  `PASSWORD` varchar(255) NOT NULL,
  `EMAIL` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`NICKNAME`),
  UNIQUE KEY `ID` (`ID`)
) ;

This table already exists and was created without any problems. I Want to create a score Table like this:

CREATE TABLE IF NOT EXISTS `scores` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `NICKNAME` varchar(50) NOT NULL,
  `HIGHSCORE` int(11) NOT NULL,
  PRIMARY KEY (`ID`),
  FOREIGN KEY (NICKNAME) REFERENCES USER(Nickname)
)

On execution of the query I get this errormassage:

**#1005 - Kann Tabelle `xxxxx`.`scores` nicht erzeugen (Fehler: 150 "Foreign key constraint is incorrectly formed") (Details…)**

Its in German and says cant create Table, Error 150, I cant see where the key constraint is wrong, I used the same syntax in postgreSQL and it worked fine, but somehow MySQL is not accepting it. Any Ideas?

Answer 1

That is strange. If nickname is indeed the primary key, then your code should work.

It is much more nature, though, to use the auto-incremented column as the primary key. If you want the nickname, then use a join when you query.

So:

CREATE TABLE IF NOT EXISTS `scores` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  UserId int(11) NOT NULL,
  `NICKNAME` varchar(50) NOT NULL,
  `HIGHSCORE` int(11) NOT NULL,
  PRIMARY KEY (`ID`),
  FOREIGN KEY (UserId) REFERENCES USER(Id)
);

Answer 2

user - is a keyword.

It may be a good idea to use another table name eg "tblUser", or use quotes again ``

FOREIGN KEY (NICKNAME) REFERENCES `USER`(ID) 

Answer 3

Thanks to Mr. Gordon Linoff I was able to find my Mistake:

I had to declare NICKNAME to be declared UNIQUE, only then the FOREIGN KEY constraint could be added to other tables

CREATE TABLE IF NOT EXISTS `user` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `NICKNAME` varchar(50) NOT NULL,
  `PASSWORD` varchar(255) NOT NULL,
  `EMAIL` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`NICKNAME`),
  UNIQUE KEY `ID` (`ID`),
  UNIQUE KEY `NICKNAME` (`NICKNAME`)
);