CREATE TABLE main_category(
id_main_category INT NOT NULL AUTO_INCREMENT ,
title VARCHAR( 50 ) NOT NULL ,
description VARCHAR( 500 ) NOT NULL ,
PRIMARY KEY ( id_main_category )
)ENGINE=myisam;


CREATE TABLE sub_category(
id_sub_category INT NOT NULL AUTO_INCREMENT ,
title VARCHAR( 50 ) NOT NULL ,
description VARCHAR( 500 ) NOT NULL ,
PRIMARY KEY ( id_sub_category )
)ENGINE=myisam;


CREATE TABLE category(
id_category INT NOT NULL AUTO_INCREMENT ,
id_sub_category INT NOT NULL,
id_main_category INT NOT NULL,
PRIMARY KEY ( id_category ), 
FOREIGN KEY (id_sub_category) REFERENCES 
sub_category(id_sub_category),
FOREIGN KEY (id_main_category) REFERENCES main_category(id_main_category)
)ENGINE=myisam;