[Deprecated] DMZ 1.5.3 (DataMapper OverZealous Edition)

[eluser]NachoF[/eluser]
[quote author="OverZealous.com" date="1241686440"][quote author="NachoF" date="1241685205"]I keep reading about these "self references"... sorry to ask such a n00b question but what are they and when would be a good time to use them??.... Im trying to learn as much as I can cause I have been hired to make a project (and its pretty much done already) but if I want to stay in this business for more future projects I guess I have to learn more and more still... (I still pretty much suck at HTML+CSS as well.)[/quote]

A self reference refers to when an item must store a reference to another item of the same type. Think of a file hierarchy. A folder can contain files, but it also can contain other folders. The relationship between two folders would be a self reference.

Other common self references:
* An Employee has a Boss (who is also an Employee).
* An Article is related to other similar Articles.
* A Bugfix depends on other Bugfixes before it can be completed.

Generally speaking, self references should be avoided unless they describe something that is recursive. In the case of MeanStudios' problem, I don't think it is actually recursive.

What makes them special, specifically for DataMapper, is (1) that they use the same table to store data, and (2) that they would have the same name on both sides of the relationship. Luckily, most relationships have a non-uniform connection, meaning, Parent->Child or Boss->Employee has a different meaning in each direction.

However, in the example of Article<->Article, the direction of the relationship does not matter. This is not something that can be described easily in a Database, and DMZ does not provide any tools for this kind of relationship. The best you can do is either modify it so it can be defined in unidirectional manner, or save the relationship twice, once for each direction.

In the original DataMapper, the only way to have something like a self-reference was to have two different models, which broke a lot of things. In DMZ, I let you specify all of the relationship fields manually (which is why they are a little confusing), so you can create very complicated relationships.

I don't know what your education background is, but if you can, I recommend taking a class on relational database management, since much of data storage is based on that. If a class isn't possible, try looking for books in your local Library. I find data storage to be difficult to learn without being hands-on.[/quote]
Im studying "Systems Engineering" but its really more about management and costs than actually learning about good programming practices... I live in Venezuela and my college is pretty much for students of the far right that are formed to just be managers and not really part of the workforce... but I personally am very interested in how to get things done and not just being a project manager..... back to the topic though, so "self-referencing" is like hierarchy when it comes to classes in OOP???.. please elaborate more in your first example... say I have employees and a boss... how would I structure a sql database to have them all in the same table?.....
Edit:
Thinking about it a little more Im guessing the employee table would have a field "boss_id" that would actually be the employee_id that is the boss of that employee, right?... and the actual boss would just have himself or null, right?