Forum Threads Table Design

[compsci]

Hello all,

I am using MySQL version: 5.0.37

I am creating a forum. I am designing the tables for the threads and their replies and the relationship between them. Please have a look at these images and give me your thoughts. I have also included the schema.

http://i284.photobucket.com/albums/ll40/JavaPHPNinja/threadsTableDesign.jpg
http://i284.photobucket.com/albums/ll40/JavaPHPNinja/threadsLogicDesign.jpg

CREATE TABLE  Threads (
       threadID INT NOT NULL AUTO_INCREMENT
     , threadSubject VARCHAR(100) NOT NULL
     , threadContent TEXT NOT NULL
     , link VARCHAR(200)
     , poster VARCHAR(100) NOT NULL
     , PRIMARY KEY (threadID)
);

CREATE TABLE  ThreadReplies (
       replyID INT NOT NULL AUTO_INCREMENT
     , replySubject VARCHAR(100)
     , replyContent TEXT NOT NULL
     , poster VARCHAR(100) NOT NULL
     , PRIMARY KEY (replyID)
);

CREATE TABLE  ThreadsRepliesRelationship (
       threadID INT NOT NULL
     , replyID INT NOT NULL
     , INDEX (threadID)
     , CONSTRAINT ThreadsFK FOREIGN KEY (threadID)
                  REFERENCES  Threads (threadID) ON DELETE CASCADE
     , INDEX (replyID)
     , CONSTRAINT RepliesFK FOREIGN KEY (replyID)
                  REFERENCES  ThreadReplies (replyID) ON DELETE CASCADE
);

1) Is the on cascade correct, i have them in both tables? If a thread reply was deleted would it delete the actual thread - the first post?

Thanks all, :)