Question

This seems to be a very common problem but I can’t seem to find an answer despite of all the posts and pseudotutorials I have read in the last 2 days :/

The project I am currently working on forces me to learn how to use MySQL and I seem to have run into a problem concerning ForeignKeys or Indexes.

I have these creates:
http://paste.ubuntu.com/1503473/

Edit: Inserting crutial part here cause the link above might die sometime:

   CREATE TABLE user_book (
        userid  Varbinary(16),
        bookid Varbinary(16),

        PRIMARY KEY(userid, bookid),

        INDEX(userid),
        FOREIGN KEY(userid)  REFERENCES user,

        INDEX (bookid),
        FOREIGN KEY(bookid) REFERENCES book

    )ENGINE=INNODB;

    Made the same mistake at user_chapter.

But sql throws an error at Table “user_book”:
#1005 – Can’t create table ‘mangressdb.user_book’ (errno: 150)

It would be really great if you could help me out here as I am close to crying. It is probably just a very stupid mistake on my part but I can’t find it.

Answer 1

Looks like you are getting name conflicts in your DDL. Try explicitly specifying the parent table columns to be used for the foreign keys:

CREATE TABLE user_book (
    userid  Varbinary(16),
    bookid Varbinary(16),

    PRIMARY KEY(userid, bookid),

    INDEX(userid),
    FOREIGN KEY(userid)  REFERENCES user (userid),

    INDEX (bookid),
    FOREIGN KEY(bookid) REFERENCES book (bookid)

)ENGINE=INNODB;

You will need to also explicitly specify the parent column names for your user_chapter table.