FK reference PK in same table

[julien-martin]

Hello,

I have two questions:

1. I have a table defined as follows
*********************************************
create table MATABLE  (
   ID                   INTEGER                         not null,
   FK                   INTEGER                        not null,
   constraint PK_MATABLE primary key (ID)
);

alter table MATABLE
   add constraint FK_MATABLE_REFERENCE_MATABLE foreign key (FK)
      references MATABLE (ID);
*********************************************
I understand the FK reference the PK in the same table. My first question is can 
anybody give me a practical example of having the above architecture/relation. A 
sample of a few lines together with a short explanation would be great.

2. The above script has been generated for Oracle. Can anyone tell me how to make it 
work for MySQL 4?

Thanks in advance,

Julien.