Relações de tabela do MyISAM Engine (MySQL)

• Aplicando chaves estrangeiras programaticamente no MySQL
• Emulando operações em cascata De InnoDB para tabelas MyISAM

Exemplo MyIsam com chave estrangeira:

CREATE TABLE myisam_parent
(
 mparent_id INT NOT NULL,
 PRIMARY KEY (mparent_id)
) ENGINE=MYISAM;

CREATE TABLE myisam_child
(
 mparent_id INT NOT NULL,
 mchild_id INT NOT NULL,
 PRIMARY KEY (mparent_id, mchild_id)
) ENGINE = MYISAM;

DELIMITER $$
CREATE TRIGGER insert_myisam_child
BEFORE INSERT ON myisam_child
FOR EACH ROW
BEGIN
    IF (SELECT COUNT(*) FROM myisam_parent WHERE mparent_id=new.mparent_id)=0 THEN
        INSERT error_msg VALUES ('Foreign Key Constraint Violated!');//Custom error
    END IF;
END;$$
DELIMITER ;

Caso de teste:

INSERT INTO myisam_parent VALUES (1), (2), (3);
INSERT INTO myisam_child VALUES (1,1), (1,2), (2,1), (2,2), (2,3), (3,1);