Question

I have a table that looks like so:

CREATE TABLE `countrytable` (
  `countryCode` varchar(2) NOT NULL DEFAULT '',
  `currencyCode` varchar(3) NOT NULL,
  `currencySymbol` varchar(4) NOT NULL DEFAULT '',
  `currencyIsRight` tinyint(4) DEFAULT '0',
  `currencyName` varchar(45) DEFAULT 'US Dollar',
  `countryName` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`countryCode`,`currencyCode`),
  UNIQUE KEY `countryCode_UNIQUE` (`countryCode`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

I am trying to create another table, which has a foreign key on countrytable.currencyCode. I keep getting the following error:

The specified relation was unable to be created.
MySQL said: Can't create table 'noteitdb.#sql-b8_13' (errno: 150)

The data types of the two columns exactly match. What could I be missing?

Answer 1

ALTER TABLE `countrytable`   
  DROP PRIMARY KEY,
  ADD PRIMARY KEY (`currencyCode`, `countryCode`);

currencyCode should be indexed first. Refer MySQL docs.