phpHoo, Part I

    mysql> create table Links (
           LinkID bigint(21) NOT NULL auto_increment,
           CatID bigint(21) NOT NULL,
           Url varchar(255) NOT NULL,
           LinkName varchar(64) NOT NULL,
           Description varchar(255) NOT NULL,
           PRIMARY KEY (LinkID),
           UNIQUE (Url)
           );

mysql> insert into Categories (CatName) values ('Art');
mysql> insert into Categories (CatName) values ('Computers');
mysql> insert into Categories (CatName) values ('Religion');

mysql> select * from Categories;
+-------+--------------+-----------+
| CatID | CatName      | CatParent |
+-------+--------------+-----------+
|     1 | Art          |      NULL |
|     2 | Computers    |      NULL |
|     3 | Religion     |      NULL |
+-------+--------------+-----------+
3 rows in set (0.01 sec)

mysql> select * from Categories;
+-------+--------------+-----------+
| CatID | CatName      | CatParent |
+-------+--------------+-----------+
|     1 | Art          |      NULL |
|     2 | Computers    |      NULL |
|     3 | Religion     |      NULL |
|     4 | Dynamic HTML |         2 |
+-------+--------------+-----------+
4 rows in set (0.01 sec)

mysql> insert into Categories (CatName,CatParent) values ('E-Commerce',2);
mysql> insert into Categories (CatName,CatParent) values ('Graphics',2);
mysql> insert into Categories (CatName,CatParent) values ('Internet',2);
mysql> insert into Categories (CatName,CatParent) values ('Javascript',2);
mysql> insert into Categories (CatName,CatParent) values ('Perl',2);

mysql> select * from Categories where CatParent = 2;
+-------+--------------+-----------+
| CatID | CatName      | CatParent |
+-------+--------------+-----------+
|     4 | Dynamic HTML |         2 |
|     5 | E-Commerce   |         2 |
|     6 | Graphics     |         2 |
|     7 | Internet     |         2 |
|     8 | Javascript   |         2 |
|     9 | Perl         |         2 |
+-------+--------------+-----------+
6 rows in set (0.00 sec)

mysql> select * from Categories where CatParent IS NULL;
+-------+-----------+-----------+
| CatID | CatName   | CatParent |
+-------+-----------+-----------+
|     1 | Art       |      NULL |
|     2 | Computers |      NULL |
|     3 | Religion  |      NULL |
+-------+-----------+-----------+
3 rows in set (0.01 sec)