I am developing a website. There is an English version, Japanese version and Chinese version. Different version is for different language speakers. If you are a registered user of the English version, and you want to use the Japanese version, you still need to register on the Japanese version. So should I create one database and put all tables into this database or should I create 3 databases, each database for each version?
If these sites share no data I would say it's better to create a separate database for each. This will prevent you from accidentally damaging other version's tables if you mess up any queries.
make the tables reasonably separate, but don't close the door to possible future requirements. databases in mysql are a fine mechanism that fits both: it's a nice way to namespace the tables, and the separation is weak so you won't have problems with cross-database queries. use schemas in more sophisticated database systems.
It depends as RaYell tells on the amount of data/tables shared among these different versions. I would recommend that you look into schema support for your particular database, and partition according to schema for data separation, and by different users owning the separate schema's for security access.
In Oracle database, for example, each user is assigned it's own schema, so you could have user_en, user_jp.
Alternatively you could look into multilingual database design.
It really depends on how much data is to be shared (or combined for reporting). Even if management say "no, everything is separate" now, that'll change in 5 minutes. Always. :-)
I've worked on a number of multi-tenant systems, and would recommend a single database, designed so each site has its own ID; the negative side is the SiteID column must then be included in most of the tables, foreign keys and the associated queries. On the positive side it does allow a site's data to be extracted easily if one site is sold off, or its server is moved to a separate location for legal reasons, etc.
I'd also recommend using Unicode (or UTF-8) for all user-visible or possibly-localizable data. It'll save a lot of grief later on.
Definitely it is better to have separate databases, otherwise you will have to come up with different naming conventions for tables etc. If you have code that accesses these tables, then you will need to modify all that code as well instead of just reconfiguring the database bindings.
The answer, as usual, is "it depends." The real question, I think, is how you plan on maintaining your system.
If you are going to have a single website that allows the user to select language (or have different versions appear at different URLs), then I would use a single database, a single set of application scripts, etc. This way minor changes in schema only need to be reflected in one database. Each table with user content would have some kind of column with a SiteID column, much as devstuff recommends. A second advantage to this approach is that you can have a single user authentication system and actually let users switch from one system to another --- or eventually fuse them all together.
If you are going to have multiple applications, multiple programmers, multiple skins, etc., you may find it easier to have multiple databases. But this means that you will also have dramatically higher development costs. In some cases this is worth the trouble; in most cases it is not.
Related
I am developing a site that has many subdomains in it.
It has blogging module, management system, and many more. I have shared this question in various sites but couldn't get a proper reply.
Question is should I use one database for all the modules, this means my database would have nearly 100 tables. Is this approach be appropriate or should I create separate database for every module?
Well, it does not really matter.
If you use innodb with single data file (innodb_file_per_table setting is not enabled), then all data will be stored in a single file anyway.
With innodb separate file per table mode or with myisam table engine, the only difference between one or multiple databases is really the directory where the database files are stored. Unless the directories (databases) are located in different storage devices with different speeds, their performance will be the same.
There can be 2 reasons to keep some tables in a different database:
Security: mysql does not support role based access control. Therefore if there is a group of tables that should be accessible by a certain group of users only, then the access control is more manageable if those tables are in a different database.
If some of the modules you mentioned happen to use the same table name, then you will have to move them to a separate database or you need to modify the code and table names to avoid errors.
There is no right or wrong way to design a system. Just advantages and disadvantages to the various techniques. I normally work in Oracle and SQL Server so I had to look up some terms for MySQL. According to my research, in MySQL a database is synonymous with a schema which changes things. I'd consider these things when planning the physical design for any vendor:
Security - Do all subdomains need read/write to each other? How are the users secured? Choosing one or many schemas can impact how easy schema and user security is to manage and control.
Growth - Do some subdomains grow at a faster rate than others? If yes, I'd consider separating them to allow for the different growth rates.
Organization - Is it easier to identify the different subdomains in practice if they're separated? If you don't separate them, use a strong naming convention so you can easily identify objects within one subdomain.
Linking - How easy is it to access one schema/database from another?
Hope this helps.
I'm developing an application that will require me to create my first large-scale MySQL database. I'm currently having a difficult time wrapping my mind around the best way to organize it. Can anyone recommend any reading materials that show different ways to organize a MySQL database for different purposes?
I don't want to try getting into the details of what I imagine the database's main components will be because I'm not confident that I can express it clearly enough to be helpful at this point. That's why I'm just looking for some general resources on MySQL database organization.
The way I learned to work these things out is to stop and make associations.
In more object oriented languages (I'm assuming you're using PHP?) that force OO, you learn to think OO very quickly, which is sort of what you're after here.
My workflow is like this:
Work out what data you need to store. (Customer name etc.)
Work out the main objects you're working with (e.g. Customer, Order, Salesperson etc), and assign each of these a key (e.g. Customer ID).
Work out which data connects to which objects. (Customer name belongs to a customer)
Work out how the main objects connect to each other (Salesperson sold order to Customer)
Once you have these, you have a good object model of what you're after. The next step is to look at the connections. For example:
Each customer has only one name.
Each product can be sold multiple times to anybody
Each order has only one salesperson and one customer.
Once you've worked that out, you want to try something called normalization, which is the art of getting this collection of data into a list of tables, still minimizing redundancy. (The idea is, a one-to-one (customer name) is stored in the table with the customer ID, many to one, one to many and many to many are stored in separate tables with certain rules)
That's pretty much the gist of it, if you ask for it, I'll scan an example sheet from my workflow for you.
Maybe I can provide some advices based on my own experience
unless very specific usage (like fulltext index), use the InnoDB tables engine (transactions, row locking etc...)
specify the default encoding - utf8 is usually a good choice
fine tune the server parameters (*key_buffer* etc... a lot of material on the Net)
draw your DB scheme by hand, discuss it with colleagues and programmers
define data types based not only on the programs usage, but also on the join queries (faster if types are equal)
create indexes based on the expected necessary queries, also to be discussed with programmers
plan a backup solution (based on DB replication, or scripts etc...)
user management and access, grant only the necessary access rights, and create a read-only user to be used by most of queries, that do not need write access
define the server scale, disks (raid?), memory, CPU
Here are also some tips to use and create a database.
I can recomend you the first chapter of this book: An Introduction to Database Systems, it may help you organize your ideas, and I certainly recomend not using 5th normal form but using 4th, this is very important.
If I could only give you one piece of advice, that would be to generate test data at similar volumes as production and benchmark the main queries.
Just make sure that the data distribution is realistic. (Not all people are named "John", and not all people have unique names. Not all people give their phone nr, and most people won't have 10 phone numbers either).
Also, make sure that the test data doesn't fit into RAM (unless you expect the production data volumes to do too).
Let's say I want to build a gaming website and I have many game sections. They ALL have a lot of data that needs to be stored. Is it better to make one database with a table representing each game or have a database represent each section of the game? I'm pretty much expecting a "depends" kind of answer.
Managing 5 different databases is going to be a headache. I would suggest using one database with 5 different tables. Aside from anything else, I wouldn't be surprised to find you've got some common info between the 5 - e.g. user identity.
Note that your idea of "a lot of data" may well not be the same as the database's... databases are generally written to cope with huge globs of data.
Depends.
Just kidding. If this is one project and the data are in any way related to each other I would always opt for one database absent a specific and convincing reason for doing otherwise. Why? Because I can't ever remember thinking to myself "Boy, I sure wish it were harder to see that information."
While there is not enough information in your question to give a good answer, I would say that unless you foresee needing data from two games at the same time for the same user (or query), there is no reason to combine databases.
You should probably have a single database for anything common, and then create independent databases for anything unique. Databases, like code, tend to end up evolving in different directions for different applications. Keeping them together may lead you to break things or to be more conservative in your changes.
In addition, some databases are optimized, managed, and backed-up at a database level rather than a table level. Since they may have different performance characteristics and usage profiles, a one-size-fit-all solution may not be scalable.
If you use an ORM framework, you get access to multiple databases (almost) for free while still avoiding code replication. So unless you have joint queries, I don't think it's worth it to pay the risk of shared databases.
Of course, if you pay someone to host your databases, it may be cheaper to use a single database, but that's really a business question, not software.
If you do choose to use a single database, do yourself a favour and make sure the code for each game only knows about specific tables. It would make it easier for you to maintain things later or separate into multiple databases.
One database.
Most of the stuff you are reasonably going to want to store is going to be text, or primitive data types such as integers. You might fancy throwing your binary content into blobs, but that's a crazy plan on a media-heavy website when the web server will serve files over HTTP for free.
I pulled lead programming duties on a web-site for a major games publisher. We managed to cover a vast portion of their current and previous content, in three European languages.
At no point did we ever consider having multiple databases to store all of this, despite the fact that each title was replete with video and image resources.
I cannot imagine why a multiple database configuration would suit your needs here, either in development or outside of it. The amount of synchronisation you'll have to pull and capacity for error is immense. Trying to pull data that pertains to all of them from all of them will be a nightmare.
Every site-wide update you migrate will be n times as hard and error prone, where n is the number of databases you eventually plump for.
Seriously, one database - and that's about as far from your anticipated depends answer as you're going to get.
If the different games don't share any data it would make sense to use separate databases. On the other hand it would make sense to use one database if the structure of the games' data is the same--you would have to make changes in every game database separately otherwise.
Update: In case of doubt you should always use one database because it's easier to manage in the most cases. Just if you're sure that the applications are completely separate and have completely different structures you should use more databases. The only real advantage is more clarity.
Generally speaking, "one database per application" tends to be a good rule of thumb.
If you're building one site that has many sections for talking about different games (or different types of games), then that's a single application, so one database is likely the way to go. I'm not positive, but I think this is probably the situation you're asking about.
If, on the other hand, your "one site" is a battle.net-type matching service for a collection of five distinct games, then the site itself is one application and each of the five games is a separate application, so you'd probably want six databases since you have a total of six largely-independent applications. Again, though, my impression is that this is not the situation you're asking about.
If you are going to be storing the same data for each game, it would make sense to use 1 database to store all the information. There would be no sense in replicating table structures across different databases, likewise there would be no sense in creating 5 tables for 5 games if they are all storing the same information.
I'm not sure this is correct, but I think you want to do one database with 5 tables because (along with other reasons) of the alternative's impact on connection pooling (if, for example, you're using ADO.Net). In the ADO.Net connection pool, connections are keyed by the connection string, so with five different databases you might end up with 20 connections to each database instead of 100 connections to one database, which would potentially affect the flexibility of the allocation of connections.
If anybody knows better or has additional info, please add it here, as I'm not sure if what I'm saying is accurate.
What's your idea of "a lot of data"? The only reason that you'd need to split this across multiple databases is if you are trying to save some money with shared hosting (i.e. getting cheap shared hosts and splitting it across servers), or if you feel each database will be in the 500GB+ range and do not have access to appropriate storage.
Note that both of these reasons have nothing to do with architecture, and entirely based on monetary concerns during scaling.
But since you haven't created the site yet, you're putting the cart before the horse. It is very unlikely that a brand new site would use anywhere near this level of storage, so just create 1 database.
Some companies have single databases in the 1,000+ TB range ... there is basically no upper bound on database size.
The number of databases you want to create depends not on the number of your games, but on the data stored in the databases, or, better say, how do you exchange these data between the databases.
If it is export and import, then do separate databases.
If it is normal relationships (with foreign keys and cross-queries), then leave it in one database.
If the databases are not related to each other, then they are separate databases, of course.
In one of my projects, I distinguished between the internal and external data (which were stored in separate databases).
The difference was quite simple:
External database stored only the facts you cannot change or undo. That was phone calls, SMS messages and incoming payments in our case.
Internal database stored the things that are usually stored: users, passwords etc.
The external database used only the natural PRIMARY KEY's, that were the phone numbers, bank transaction id's etc.
The databases were given with completely different rights and exchanging data between them was a matter of import and export, not relationships.
This made sure that nothing would happen with actual data: it is easy to relink a payment to a user, but it's very hard to restore a payment if it's lost.
I can pass on my experience with a similar situation.
We had 4 "Common" databases and about 30 "Specific" databases, separated for the same space concerns. The downside is that the space concerns were just projecting dBase shortcomings onto SQL Server. We ended up with all these databases on SQL Server Enterprise that were well under the maximum size allowed by the Desktop edition.
From a database perspective with respect to separation of concerns, the 4 Common databases could've been 2. The 30 Specific databases could've been 3 (or even 1 with enough manipulation / generalization). It was inefficient code (both stored procs and data access layer code) and table schema that dictated the multitude of databases; in the end it had nothing at all to do with space.
I would consolidate as much as possible early and keep your design & implementation flexible enough to extract components if necessary. In short, plan for several databases but implement as one.
Remember, especially on web sites. If you have multiple databases, you often lose the performance benefits of query caching and connection pooling. Stick to one.
Defenitively, one database
One place I worked had many databases, a common one for the stuff all clients used and client specifc ones for customizing by client. What ended up happening was that since the clients asked for the changes, they woudl end up inthe client database instead of common and thus there would be 27 ways of doing essentially the same thing becasue there was no refactoring from client-specific to "hey this is something other clients will need to do as well" so let's put it in common. So one database tends to lead to less reinventing the wheel.
Security Model
If each game will have a distinct set of permissions/roles specific to that game, split it out.
Query Performance /Complexity
I'd suggest keeping them in a single database if you need to frequently query across the data between the games.
Scalability
Another consideration is your scalability plans. If the games get extremely popular, you might want to buy separate database hardware for each game. Separating them into different databases from the start would make that easier.
Data Size
The size of the data should not be a factor in this decision.
Just to add a little. When you have millions and millions of players in one game and your game is realtime and you have tens of thousand simultaneous players online and you have to at least keep some essential data as up-to-date in DB as possible (say, player's virtual money). Then you will want to separate tables into independent DBs even though they are all "connected".
It really depends. And scaling will be painful whatever you may try to do to avoid it being painful. But if you really expect A LOT of players and updates and data I would advise on thinking twice, thrice and more before settling on a "one DB for several projects" solution.
Yes it will be difficult to manage several DBs probably. But you will have to do this anyway.
Really depends :)..
Ask yourself these questions:
Could there be a resuability (users table) that I may want to think about?
Is it worth seperating these entities or are they pretty much the same?
Do any of these entities share specific events / needs?
Is it worth my time and effort to build 5 different database systems (remember if you are writing the games that would mean different connection strings and also present more security, etc).
Or you could create one database OnlineGames and have a table that stores the game name and a category:
PacMan Arcade
Zelda Role playing
etc etc..
It really depends on what your intentions are...
i am developing a project that its domain is meaningful in my native language. So i bought a second English domain for global usage.
My question is, how should i construct my site?
Two different projects or one project with localization support?
Two different databases or shared database?
What is my goal?
Dont want to show English content in native site, vice versa
I want to easily update site
If you suggest me to use shared database, could you please describe me design principle of database?
Thank You.
Typically for application code you ideally want to not fork for any reason including language. There are some quick things you need to watch out for;
Ensure that strings are not hardcoded
Store all datetimes in UTC
Ensure that all user profiles have an associated timezone (you can grab this from the user's browser
Try to ensure that your presentation is separate from your page content (i.e. use CSS, Master Pages, Templates or whatever your platform supports).
As for the database this depends more on the data your holding, for example if;
You want users to share logins across both sites
Knowledge to be shared but not necessarily localized (Wiki Entries)
The sites are managing a shared resource (i.e. a single warehouse)
You might want to have one database.
However if you find the following are true;
You don't want/need users between the sites to have cross over (think amazon.com and amazon.co.uk)
Knowledge is wholly separate with entries in one language being irrelevant to the other
The sites are managing wholly separate resources (i.e. two separate warehouses)
You might lean towards two separate databases. This will give you an advantage in scaling (though its not a silver bullet) and as long as the schemas are identical across the databases you will likely find that it's not too onerous.
One other option is to identify shared resources and split them into another repository (think user logins etc...). This can get you the best of both worlds but of course is a more complex design.
Remember all of this can be added after the fact it just becomes harder. Sometimes it's more important to get to market than it is to try and solve all your problems up front.
Good Luck!
I'm not quite sure what could work for you, but I think that localization support would it be nice, and if you have a shared database you won't need to support to different databases and you won't need to add an extra database anytime you need to add a new language, and thinking about the application it would be easier just to if you want another language just to add it to your configuration and not create another project just to add that.
Is it because of size?
By the way, what is the limit of the size?
There are many reasons to use two databases, some that come to mind:
Size (the limit of which is controlled by the operating system, filesystem, and database server)
Separation of types of data. Think of a database like a book -- you wouldn't write a book that spans multiple subjects, and you shouldn't (necessarily) have a database with multiple subjects. Just so all of the data is somehow related, you could keep it together (i.e. all the tables have something to do with one website or application).
Import / Export - it might be easier to import data into your application if you can drop and restore a whole database, rather than import individual rows into a database table.
Separate applications, or services. I can't see any reason to use separate databases for a single app/service.
(note: replication, even multimaster, isn't a separate database. Neither is Sharding.)
I believe some on here are confusing Database with a Database Instance.
Example:
A phone book is a prime example of a Database.
Replication:
having 2 copies of the same phone book does not mean you have 2 databases. It means you have 2 copies of 1 database, and that you can hand 1 to someone else so you can both look up different things at the same time thereby accomplishing more work at once.
Sharding:
You could tear those phonebooks apart at the end of the white pages and the beginning of the yellow and hand them to 2 more people. You could further tear them at each letter and when you need susan summers ask the person with that section of the book to look for her.
suppose you wanted to publish or reuse some external database, and keep it separate from your primary database. This would be a good reason to use 2 databases... You can drop and reimport the external database at any time without affecting your database, and vice versa...
You can use two databases the same reason most banks have two ATMs, for reliability. You can swap one in if the other fails, but to do it quickly requires setup, such as a cname and controlling your own DNS server.
You can also do writes on one database, if the writes have complex triggers on them, and use some synching between databases to keep the second one updates, which is used for selects.
You can use two databases for load sharing, for example, use round-robin to split up the load so one isn't overloaded.
I sometimes have separate database because they handle different concerns. I.E. a Reporting database or an Authentication Database.
Replication
Making your system scalable by devide your database system to different physical location
Provide redundancy/replication as backup and seamless uptime.a
As Ben mentioned, Replication is one reason. Another is load balancing.
For example, Hotmail uses many database servers and customer data is broken up across the databases.
To have all of their customers' data on one server would not only require massive storage requirements, but the response times would be horrible.
In other cases, the data may be separated by function. You may well have two sets of data which are either not connected, or at least very loosely so, and in such cases, it may make sense to separate that data from the rest.
Also consider IO needs. Writing to one, reading from the other. One with immediate transactional needs, others where "transactions" can be queued, one instance at high priority, the other at "idle" priority, &c. It is very obvious however with the correct hardware and tablespace/filesystem layouts most of these situations can be achieved in a singular DB.
I think SQLite databases on the iPhone is limited to a size of 50 megabytes, but you can open several databases.