Cannot add a foreign key in mysql where a field is a unique index - mysql

Question

I'm having problem adding a foreign key based on AUTH_ISLE_CODE:
Create Table: CREATE TABLE `AUTH_ACCOUNT` (
`ACCOUNT_ID` int(11) NOT NULL AUTO_INCREMENT,
`PASSWORD` varchar(20) DEFAULT NULL,
...
`AUTH_ISLE_ID` int(11) NOT NULL DEFAULT '1',
`AUTH_ISLE_CODE` varchar(5) NOT NULL DEFAULT 'AAAAA',
PRIMARY KEY (`ACCOUNT_ID`),
KEY `fk_ACCOUNT_ISLE` (`AUTH_ISLE_ID`),
CONSTRAINT `fk_ACCOUNT_ISLE` FOREIGN KEY (`AUTH_ISLE_ID`) REFERENCES `AUTH_ISLE` (`ISLE_ID`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=166 DEFAULT CHARSET=utf8
Create Table: CREATE TABLE `AUTH_ISLE` (
`ISLE_ID` int(11) NOT NULL AUTO_INCREMENT,
`NAME` varchar(100) DEFAULT NULL,
`CODE` varchar(5) NOT NULL DEFAULT 'AAAAA',
PRIMARY KEY (`ISLE_ID`),
UNIQUE KEY `CODE_UNIQUE` (`CODE`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8
the error I'm having is:
ERROR 1005 (HY000): Can't create table 'masterdata.#sql-73c1_57910' (errno: 150)
Is it something about the fact that the two tables have already a relationship with AUTH_ISLE_ID
Edit 1: the SHOW CREATE TABLE you see is the current situation. I'm trying to add just the constraint to AUTH_ISLE_CODE -> CODE from AUTH_ISLE

Answer 1

If this is a sequence of queries you are trying to create tables then it will always fail because you are referencing a table REFERENCES AUTH_ISLE (ISLE_ID) which is not created yet ,try creating first AUTH_ISLE table then create your second table AUTH_ACCOUNT,and when AUTH_ISLE is present you can simply reference its columns
CREATE TABLE `AUTH_ISLE` (
`ISLE_ID` int(11) NOT NULL AUTO_INCREMENT,
`NAME` varchar(100) DEFAULT NULL,
`CODE` varchar(5) NOT NULL DEFAULT 'AAAAA',
PRIMARY KEY (`ISLE_ID`),
UNIQUE KEY `CODE_UNIQUE` (`CODE`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
CREATE TABLE `AUTH_ACCOUNT` (
`ACCOUNT_ID` int(11) NOT NULL AUTO_INCREMENT,
`PASSWORD` varchar(20) DEFAULT NULL,
`AUTH_ISLE_ID` int(11) NOT NULL DEFAULT '1',
`AUTH_ISLE_CODE` varchar(5) NOT NULL DEFAULT 'AAAAA',
PRIMARY KEY (`ACCOUNT_ID`),
KEY `fk_ACCOUNT_ISLE` (`AUTH_ISLE_ID`),
CONSTRAINT `fk_ACCOUNT_ISLE` FOREIGN KEY (`AUTH_ISLE_ID`)
REFERENCES `AUTH_ISLE` (`ISLE_ID`)
ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=166 DEFAULT CHARSET=utf8;
Demo
insert into AUTH_ISLE (NAME,CODE) values('Test','Test');
insert into AUTH_ACCOUNT (PASSWORD,AUTH_ISLE_ID,AUTH_ISLE_CODE)
values('Test',last_insert_id(),'Test');
Insert Demo