Database Schema for News System - php

Question

I have a news system I'm designing, and it seemed straight-forward at first, but as I've pushed forward with my planned schema I've hit problems... Clearly I haven't thought it through. Can anyone help?
The system requires that the latest 20 news articles be grabbed from the database. It's blog-like in this way. Each article can have sub-articles (usually around 3) that can be accessed from the parent article. The sub-articles are only ever visible when the parent article is visible -- they're not used elsewhere.
The client needs to be able to hide/display news articles (easy), but also change their order, if they desire (harder).
I initially stored the sub-articles in a separate table, but then I realised that the fields were essentially the same: Headline, Copy, Image. So why not just put them all in one big table?
Now I've hit other problems around the ordering. It's Friday evening and my head hurts!
Can anyone offer advice?
Thanks.
Update: People have asked to see my "existing" schema:
articleID *
headline
copy
imageURL
visible
pageOrder
subArticleID *
articleID
headline
copy
imageURL
visible
pageNumber
pageOrder
Will this work? How would I go about letting users change the order? It seemed the wrong way to do it, to me, so I threw this out.

Answer 1

I initially stored the sub-articles in a separate table, but then I realised that the fields were essentially the same: Headline, Copy, Image. So why not just put them all in one big table?
Because referential integrities are not the same.
That is, of course, if you want to restrict the tree to exactly 2 levels. If you want more general data model (even if that means later restricting it at the application level), then go ahead and make a general tree.
This would probably look something like this:
Note how both PARENT_ARTICLE_ID and ORDER are NULL-able (so you can represent a root) and how both comprise the UNIQUE constraint denoted by U1 in the diagram above (so no two articles can be ambiguously ordered under the same parent).

Answer 2

Based on what you've described. I would use two tables. The first table would hold all the articles and sub-articles. The second would tie the articles to their sub-articles.
The first table (call it articles) might have these columns:
+-----------+----------+------+----------+---------+------------+-----------+
| articleID | headline | copy | imageURL | visible | pageNumber | pageOrder |
+-----------+----------+------+----------+---------+------------+-----------+
The second table (call it articleRelationships) might have these columns:
+-----------------+----------------+
| parentArticleID | childArticleID |
+-----------------+----------------+
Not sure if you already accomplish this with the pageNumber column, but if not, you could add a column for something like articleLevel and give it something like a 1 for main articles, 2 for sub-articles of the main one, 3 for sub-articles of a level 2 article, etc. So that way, when selecting the latest 20 articles to be grabbed, you just select from the table where articleLevel = 1.
I'm thinking it would probably also be useful to store a date/time with each article so that you can order by that. As far as any other ordering goes, you'll have to clarify more on that for me to be more help there.
To display them for the user, I would use AJAX. I would first display the latest 20 main articles on the screen, then when the user chooses to view the sub-articles for a particular article, use AJAX to call the database and do a query like this:
SELECT a.articleID, a.headline
FROM articles a
INNER JOIN articleRelationships ar ON a.articleID = ar.childArticleID
WHERE ar.parentArticleID = ? /* ? is the articleID that the user clicked */
ORDER BY articleID

Answer 3

The client needs to be able to hide/display news articles (easy), but
also change their order, if they desire (harder).
On this particular point, you'll need to store client-specific ordering in a table. Exactly how you do this will depend, in part, on how you choose to deal with articles and subarticles. Something along these lines will work for articles.
client_id article_id article_order
--
1 1067 1
1 2340 2
1 87 3
...
You'll probably need to make some adjustments to the table and column names.
create table client_article_order (
client_id integer not null,
article_id integer not null,
article_order integer not null,
primary key (client_id, article_id),
foreign key (client_id) references clients (client_id) on delete cascade,
foreign key (article_id) references articles (article_id) on delete cascade
) engine = innodb;
Although I made article_order an integer, you can make a good case for using other data types instead. You could use float, double, or even varchar(n). Reordering can be troublesome.
If you don't need the client id, you can store the article ordering in the article's table.
But this is sounding more and more like the kind of thing Drupal and Wordpress do right out of the box. Is there a compelling reason to reinvent this wheel?

Answer 4

Create a new field in news(article) table "parent" which will contain news id of parent article. This new field will be used as a connection between articles and sub articles.

Answer 5

As SlideID "owns" SubSlideID, I would use a composite primary key for the second table.
PrimaryKey: slideID, subSlideID
Other index: slideID, pageNumber, pageOrder (Or however they get displayed)
One blog post I prefer to point out about this is http://weblogs.sqlteam.com/jeffs/archive/2007/08/23/composite_primary_keys.aspx as it explains why very nicely.
If you're replying on Auto_Increment, that can be handled too (with MyISAM tables), you can still set subSlideID to auto_increment.
If you're likely to go to a third level then merge - follow Branko above. But it does start to get very complicated, so keep separate for 2 layers only.