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Editorial Team
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Asked: 2026-05-23T10:10:47+00:00

I have the following SQL script. After it runs the foreign key relationship is

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I have the following SQL script. After it runs the foreign key relationship is never enforced.

CREATE TABLE Country (
  name varchar(40) NOT NULL,
  abbreviation varchar(4) NOT NULL,
  PRIMARY KEY  (name)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8;

CREATE TABLE StateProvince (
  countryName varchar(40) NOT NULL,
  name varchar(100) NOT NULL,
  abbreviation varchar(3) NOT NULL,
  PRIMARY KEY  (countryName,name)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

alter table StateProvince
add index FK_StateProvince_Country (countryName),
add constraint FK_StateProvince_Country
foreign key (countryName)
references Country (name);

Is this because of the composite primary key?

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1 Answer

  1. Editorial Team

    According to the MySQL docs on foreign keys, The MyISAM table engine does not support foreign keys. Instead it silently ignores them. Use InnoDB instead. Try this:

    CREATE TABLE Country (
  name varchar(40) NOT NULL,
  abbreviation varchar(4) NOT NULL,
  PRIMARY KEY  (name)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8;

CREATE TABLE StateProvince (
  countryName varchar(40) NOT NULL,
  name varchar(100) NOT NULL,
  abbreviation varchar(3) NOT NULL,
  PRIMARY KEY  (countryName,name)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

alter table StateProvince
add index FK_StateProvince_Country (countryName),
add constraint FK_StateProvince_Country
foreign key (countryName)
references Country (name);
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