I'm trying to make a table and mysql is giving me this error:

#1005 - Can't create table 'likes.users' (errno: 150)

That would be great to see a website that explains mysql errors like this for oracle http://ora-code.com/

CREATE TABLE IF NOT EXISTS `users` (
 `user_id` int(2) NOT NULL AUTO_INCREMENT,
 `username` varchar(20) NOT NULL,
 `article_id` int(11) NOT NULL,
 PRIMARY KEY (`user_id`),
 CONSTRAINT `fk_article_id` FOREIGN KEY (`article_id`) REFERENCES `articles` (`article_id`)  ON DELETE SET NULL ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=latin1

I can't see anything wrong with the create statement.

I personally don't see anything wrong with the syntax or the foreign keys that I am trying to make. Can you pick any error in the create statement?

Thanks, pal.

Yes, I do have another table called articles. Therefore, mySQL server shouldn't refuse my request.

Perhaps a mismatch in columns types (guessing here) ? Is there already data in articles ?

It doesn't contain any data.

I just tried to run the following on my test database, and it executes just fine.

CREATE TABLE IF NOT EXISTS `articles` (
  `article_id` INT(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`article_id`)
) ENGINE=INNODB DEFAULT CHARSET=latin1;

CREATE TABLE IF NOT EXISTS `users` (
  `user_id` INT(2) NOT NULL AUTO_INCREMENT,
  `username` VARCHAR(20) NOT NULL,
  `article_id` INT(11) NOT NULL,
  PRIMARY KEY (`user_id`),
  CONSTRAINT `fk_article_id` 
    FOREIGN KEY (`article_id`) 
    REFERENCES `articles` (`article_id`)  
    ON UPDATE CASCADE
) ENGINE=INNODB AUTO_INCREMENT=12 DEFAULT CHARSET=latin1;

The ON DELETE SET NULL is not possible. Your article_id is set to NOT NULL. This is causing the issues.

From line 11 to 14, Would that be problematic to have all these SQL statements on just one line? (that is what I initially had)

What does this line mean? AUTO_INCREMENT=12?

No, spacing doesn't matter, I just added that for readability.

That means the next auto id generated will be 12, remove that if you want to start at 1 again.

Thanks for explainin that to me. Now, I created the foreign keys that I needed for the tables. However, I was unable to add/specify restriction on the keys. ON UPDATE CASCADE ON DELETE SET NULL .. I don't know why mysql isn't happy to accept my commands.

I don't want to recreate the FKs. I just want to modify them to add these properties in ON DELETE SET NULL and so on. Is there a modify-constraint statement?

If you change `article_id` INT(11) NULL in users then it should work.

I created the foreign key on article_id. But, I couldn't specify this property at the time of creation. ON UPDATE CASCADE.