MySQL MariaDB wont create Table with a foreign key - mysql

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 e.g. "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`)
);