BBS tree structure Table Design

Create Database BBS;

Use BBS;

Create Table article
(
Id int primary key auto_increment,
PID int,
Rootid int,
Title varchar (255 ),
Cont text,
Pdate datetime,
Isleaf int
);

Insert into article values (null, 0, 1, 'Ant vs. elephant ', 'Ant vs. elephant', now (), 1 );
Insert into article values (null, 1, 1, 'elephant knocked down ', 'elephant knocked down', now (), 1 );
Insert into article values (null, 2, 1, 'Ant is not too bad ', 'Ant is not too bad', now (), 0 );
Insert into article values (null, 2, 1, 'taobao', 'taobao', now (), 1 );
Insert into article values (null, 4, 1, 'no taobao', 'no taobao', now (), 0 );
Insert into article values (null, 1, 1, 'How possible ', 'How possible', now (), 1 );
Insert into article values (null, 6, 1, 'How is it impossible? ', 'How is it impossible?', now (), 0 );
Insert into article values (null, 6, 1, 'likelihood is great ', 'likelihood is great', now (), 0 );
Insert into article values (null, 2, 1, 'elephant in hospital ', 'elephant in hospital', now (), 1 );
Insert into article values (null, 9, 1, 'nurse is ant', 'nurse is ant', now (), 0 );