Foreign key error

Question

why the foreign key gives my headache?
first i created database names colorcode then paper table which works fine:

CREATE TABLE paper (
  paper_id int(20) NOT NULL,
  description VARCHAR(40) NOT NULL,
  paper_color VARCHAR(40) NOT NULL,
  PRIMARY KEY (paper_id, paper_color)
) ENGINE=InnoDB;

then brick table

CREATE TABLE brick(
  brick_id int(20) NOT NULL,
  description varchar(40) NOT NULL,
  brick_color varchar (40) NOT NULL,
  PRIMARY KEY (brick_id),
  FOREIGN KEY (brick_color) REFERENCES paper(paper_color)
) ENGINE=InnoDB;

which doesn't=>

#1005 - Can't create table 'colorcode.brick' (errno: 150)

thank you for your help

Answer 1

Create a separate key for paper_color and it will work:

CREATE TABLE paper (
    paper_id int(20) not null,
    description VARCHAR(40)not null,
    paper_color VARCHAR(40) NOT NULL,
    PRIMARY KEY (paper_id, paper_color),
    KEY (paper_color)
) ENGINE=InnoDB;