CREATE TABLE question (
id int(10) unsigned NOT NULL AUTO_INCREMENT,
title varchar(150) NOT NULL DEFAULT '',
body text NOT NULL,
PRIMARY KEY (id),
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE answer (
id int(10) NOT NULL,
body text NOT NULL,
questionId int(10) NOT NULL DEFAULT '0',
PRIMARY KEY (id),
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE comment (
id int(10) NOT NULL,
body varchar(255) NOT NULL,
itemType tinyint(3) unsigned NOT NULL DEFAULT '0', // 1 => 'question', 2=> 'answer'
itemId int(10) unsigned NOT NULL DEFAULT '0', // questionId or answerId
PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
as related comments determined by itemType and itemId, how to define the relationship between question-comment or answer-comment?