I have 3 types of content: blogs, press releases, and reminders. All of them have a body and entered by fields. The blogs and press releases have a title field, which the reminder lacks, and the reminders has an hour field, which blogs and press releases lack. This is what it looks like in tabular format so it's easy for you to see...
blog press release reminder
---------------------------------------------------
entered by field yes yes yes
body field yes yes yes
title field yes yes --
time field -- -- yes
I'm creating a main table called content that links to the specialized tables blogs press releases reminders. I thought of 2 structures
First structure... This is how the content management system I use does it, but I don't want to follow in their steps blindly because my needs are not the same. Put ALL shared fields in the main content table. So the content table will not only have type and type id to link to the specialized tables, the content table will also have the common fields like body and entered by. The other 3 tables only have their unique fields.
content table B=blogs table PR=press releases table R=reminders table
------------------------------------------------------------------------------
id id id id
type=B/PR/R title title hour
type id
body
entered by
Second structure. content table only has the type and type id necessary to link to the other 3 tables, This means that the common fields get repeated in the 3 tables.
content table B=blogs table PR=press releases table R=reminders table
------------------------------------------------------------------------------
id id id id
type=B/PR/R entered by entered by entered by
type id body body body
title title hour
Which should I go with? I thought the first structure is better because I can search all content whether it's a blog or press release or reminder for a specific word. I still have to look in the other tables if I want to search the title which is available only to blogs and press releases, but...
So which structure is better, and why you think so? I'm also open to other ideas or improvements that are different from these 2.
The first structure is a classic super type-subtype approach, and recommended. I would just suggest naming primary keys with full table-name-id like ContentID to avoid possible confusion.
The first one is the better construct, it allows for a content to have a specific set of required or common data in the content table and then specialized data in the child tables. This also allows you to add more types in the future with other requirements that still reuse the common elements in content but retain any unique data.
One other key question is if that data is required, for example do all reminders require an hour and do all blogs/press release require a title. If they are required then you ensure that those child tables will always be populated. If they are not then perhaps you should look at flattening the structure (yes Virginia you should sometimes denormalize).
So instead your content table simply becomes (nn = not null, n = nullable)
id (nn) ,type id (nn), type (nn), body (nn), entered by (nn), title (n), hour (n). The main reason I usually find for doing this is that if the different data entities you are creating are so similar that over time it is possible they will merge. For example reminders at this time do not require a title, but in the future the might.
I would sooner go without any sort of "type" field, instead making four tables: content, blogs, pressreleases and reminders. Content has the common fields enteredby, body, and title. For each of blogs, pressreleases and reminders, they have an id that is a primary key and also a foreign key to a content id. This makes a 1:1 "is-a" relationship. reminder can have the additional time field. To determine what type of entry a content row is, do a join select.
This may not be the best in terms of performance but it's better normalized.
I think you should think about the common fields.
Do they really need to match?
If they need to match, it's easier to just put it in a single table.
Related
If one post has many comments, and the comments are essentially the same as posts (e.g. they have a title, pictures and audio etc.) should I create two tables or just one?
For example, if I only use one table I can have a parent_id column, so If it's not a reply to anything it would be null, otherwise, it would have the id of the parent post. On the other hand I can create a post table and a comments table. Comments can also reply back to other comment so this could get confusing quick.
*Post*
id
title
content
image
audio
parent_id
or,
*Post* *Comments*
id id
title title
content content
image author_id
audio post_id
author_id image
audio
What the second option would allow is creating indexes. Infact I won't even have to add author_id or post_id If I use indexes from the start will I?
What are you thoughts on this SO? Which would be more efficient? I thinking of using redbeanphp for this.
The second option would be better. When displaying a message board, you don't care about comments and looking them up by an indexed parent post id column is fast. Posts and comments will likely have different fields, so keeping them separate is correct. The parent id index for the first option would work fine, but conceptually, it's messy and you're basically creating an index to use on half or however many comments there are relative to posts.
As a rule in database-design: Tables are called entities, so each entity in your application should be separated and demonstrated by table. Here, although you regarded posts and comments each has the same kind of data but finally each of them is a separate entity so they should be separated in two tables. This behavior is not a personal opinion. It is basic rule that leads to more smooth application development.
I am currently working on a system that would allow users to add additional custom fields for the contacts that they add.
I wondered what is the best and most efficient approach to add such ability?
Right now what I was thinking was to have 1 table per users (with foreign keys to a "main" contacts table) and then adding a column for each custom fields that the user adds (since I don't expect to have more then 100-200 users per database shards [sharding is easy since every users never see each-other's content in this system]), although I am not 100% sure that this would be the right solution for such problems.
Maybe you could try to have one separated table to store a reference to the user, plus the field name and value, this way you will be able to have lots of custom fields.
If you go with Boyce-Codd, you separate the information and store them into a table.
Means one table for all users with a foreign key.
One table per user would lead to hundreds or more tables with possible repeated information.
You need to have one table named USERS that stores the id of a user and fixed info you might want. Then, you could have a CONTACT table, that stores the type of contact user might create, and one matching table USER_CONTACT that matches the user unique id with the id of the contact that was created.
With this, you could have advanced data mining on all the information stored, like nowing how many contacts each user created, who created more, etc...
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.
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).
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
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?
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.
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.
In a web form i will ask the user for their job experiences, this data will have no fixed lenght. I need to let the user insert all the items he needs, every item will content 3 fields; job title, description and year.
My firts problem is, how can i ask in the html form for the items? i mean, whats the best way to ask items with no fixed lenght using html/php (and maybe ajax)? I saw some sites that have a button (add one) when you hit it a new item slot is showed, but i have no idea of how to implement this, an example will be sufficient.
The second part is, how can i managed the data flow in post or get?, until now, i only use fixed fields, so i always know in my php script how many post or get vars i will get. How can i use multiple POST vars without knowing the amount of them?
And the last one (and the more important), how will be the best structure for my table in MySQL? If i get multiple items for a fixed table where i will have all my users, how can i resolve the multiple items issue? For example, if my table is:
User | password | job_experiences
admin | root | (this is just a cell, how can i save multiple items here?)
jonh | 1234 | (this is just a cell, how can i save multiple items here?)
Thanks for any help!!!!
Those are 3 questions, and it's best to post 3 questions, instead of discussing all of them. I will post the basics, and if you have specific questions, ask.
First, use button to add, and a JavaScript to clone an existing row (which can have more then one input field). For fieldnames use something like company_name[] - the [] is the important part, at this will send the field as an array. If you are editting profile, you can use company_name[$id] to preserve the mapping.
Second, in PHP you will receive this as $_POST['company_name'] which will be numeric array with all the company names. Or if you specify $id - with the corresponding keys. So, you have to loop trough all company_names, if there are other fields - you retrieve them the same way, using the current key. Example:
for (i =0; i<$_POST['comany_name'].length;i++) {
$company = $_POST['comany_name'][$i];
$start_year = $_POST['from'][$i];
...
}
Next, you need 1 table for the users (username, password), and another for job experiences (userid, company, description, from, to). This is called 1:M relation
I have read other answers on this (or at least near to this) subject but I couldn't get a clear view of it so I'm asking for help again.
I have a complex dynamic HTML form that I would like to submit to database using PHP. The form is split into multiple tabs and in each tab I got checkboxes that trigger other parts of the form. Example: at a point in my form I got a checkbox group that has options of: "hotel" and "restaurant". If I check hotels, I get another part of the form displayed, specific for "hotels". Same thing for "restaurant". So it's very dynamic here and I don't know which would be the best approach for storing every form field in database. Because it could contain 15 fields or 20, depending on the selection. Any example would be appreciated as I'm not that advanced with database design.
Thank you!
So it's very dynamic here and I don't
know which would be the best approach
for storing every form field in
database.
I apologise if I have misunderstood you here but I believe that you should design the database according to the data and not the form. It is difficult to comment without knowing the exact details of your situation so here is an example:
If you usually dump all the data from a form into a single table, but because sometimes this will involve submitting 5 values and other times this will involve submitting 10 and so you are unsure how many columns your table should have, then I think the problem is in the database design.
Work out what pieces of data are dependent on other pieces of data. For example, you mention checking "hotel" might open up more fields specific to that choice. Let's assume this involves things like "en-suite", "bed type" etc. Then you should have 3 tables, a registration table (assuming the user is using the form to buy these services), a hotel table and a registration_hotel table. The registration table will record a number of details specific to the registration only such as the customer's name and a unique id number. The hotel table will hold information specific to the hotel only, such as how many rooms have en-suite. The registration_hotel table will hold details specific to that registration at that hotel. You might want a column of type bool to record whether the user requested "en-suite".
When submitting the form, check which pieces the user entered with if(isset($_POST['hotel']) && !empty($_POST['hotel'])). Then only send stuff to the registration_hotel table if that condition is true.
If this design results in making too many separate calls to the database, you might want to look into transactions which will help you to manage the speed and security of these calls.
If you can post in a specific example of something you don't know how to do, that would be useful.
You didn't specify how you can manage this dynamic form. Can you edit it's PHP/HTML source? One great thing would be if you can label your different variables like hotel[], restaurant[], etc.
If your submitted form is clear enough (i mean semantically correctly structured) you can store the whole submitted form serialized.
Note: this method only working when you don't need to search for specific items in your database.
Edit: maybe i'm misunderstood your problem.
You can create a 'metadata' table like this:
form_id | option_name | option_value
---------------------------------------
1 | hotel | true
1 | restaurant | false