Little question, I'm developing a saas software (erp).
I designed it with 1 database per account for these reasons :
I make a lot of personalisation, and need to add specific table columns for each account.
Easier to manage db backup (and reload data !)
Less risky : sometimes I need to run SQL queries on a table, in case of an error with bad query (update / delete...), only one customer is affected instead of all of them.
Bas point : I'm turning to have hundreds of databases...
I'm hiring a company to manage my servers, and they said that it's better to have only one database, with a few tables, and put all data in the same tables with column as id_account. I'm very very surprised by these words, so I'm wondering... what are your ideas ?
Thanks !
Frederic
The current environment I am working in, we handle millions of records from numerous clients. Our solution is to use Schema to segregate each individual client. A schema allows you to partition your clients into separate virtual databases while inside a single db. Each schema will have an exact copy of the tables from your application.
The upside:
Segregated client data
data from a single client can be easily backed up, exported or deleted
Programming is still the same, but you have to select the schema before db calls
Moving clients to another db or standalone server is a lot easier
adding specific tables per client is easier (see below)
single instance of the database running
tuning the db affects all tenants
The downside:
Unless you manage your shared schema properly, you may duplicate data
Migrations are repeated for every schema
You have to remember to select the schema before db calls
hard pressed to add many negatives... I guess I may be biased.
Adding Specific Tables: Why would you add client specific tables if this is SAAS and not custom software? Better to use a Postgres DB with a Hstore field and store as much searchable data as you like.
Schemas are ideal for multi-tenant databases Link Link
A lot of what I am telling you depends on your software stack, the capabilities of your developers and the backend db you selected (all of which you neglected to mention)
Your hardware guys should not decide your software architecture. If they do, you are likely shooting yourself in the leg before you even get out of the gate. Get a good senior software architect, the grief they will save you, will likely save your business.
I hope this helps...
Bonne Chance
I'm building up an online (paid) service used for business administration purposes. The database is structured like so:
I have a contacts table filled with persons, contact info and the like. Then I have a few other tables holding information about payments, agreements and appointments. Also statistics like how much money was transferred this month, how many hours worth of appointments this month and the like.
I'm using MySQL (but could also go for MSSQL or some other service if necessary) and I had no formal training in any programming language whatsoever (yet).
I'm building a WPF application for acces to this database. Also planning on building an app so users can access their data and plan new appointments and register payments on the go.
I'm going to go for a login system to verify their right to login and use my service.
My question is about how to structure this. I'm not an SQL expert nor have I had any formal training in SQL or any other programming language. What I do know though is that my client-side app is almost out of the alpha stage.
So far I have come up with two ways to structure this.
1. Users get a seperate database.
My original idea was to give each user a seperate database, this makes it easier to provide people with statistics. Also it makes it easier to spread the workload through multiple, seperate servers. People would login to a master/main server, where their login information is stored, fetch their server info and programatically be 'redirected' to their own database. Spreading these databases also make it easier to provide individual back-ups to users.
The down-side of this is the sheer quantity of databases I'd have to manage. I'm planning on ending up with hundreds of thousands of users. Let's just say I want the system to be able to provide to an infinite amount of users.
2. Everything is stored in one database.
It's also possible to store everything in one database. This would make the database structure somewhat more complicated (while it also makes the whole a lot simpler). I'd have to add 'AND consumer_ID='" + MyID + "' to every query. (Which ofcourse is possible) and add a few tables to handle statistics per user.
It would be simpler to provide every user with the same database updates. Maintenance would be easier.
The down-side of this is that it makes it harder to spread the workload to seperate servers, I'd have to build something to make it possible that seperate servers mirror each other. Also I'd have to make sure that the workload is automatically divided between the servers, instead of simply going for: Fill server with X databases, then new server, fill, new etc.
I'm not in the luxury of hiring someone with any SQL training.
The most important thing for me now is that the system can be easily maintained while still being safe and reliable. I'm an amateur developer, going to college next year. I don't want to spend 50% of my time maintaining the database.
I think I got the major part of the details you might need, if you need anymore please ask for them.
I thank you in advance :)
Just go with solution 2. The downside of spreading the workload to many servers is fullfilled by "partitioning", look here for a starting point: http://dev.mysql.com/doc/refman/5.1/en/partitioning-overview.html
Partitioning would allow you for example to put all information of a table containing even IDs for consumers on the one, all other on the second server. Or whatever you want...
But i wouldn't start that complicated: do you need that now? It burdens you (either way) with such a big additional overhead! You can also look into the NoSQL database world for solutions that can be spread to as many servers as you want with low effort. You loose SQL and it's ACID features in the most cases; if you need those NoSQL is not an option.
I've been asked to develop an application that will be run out to a number of business units. the application will be the basically the same for each unit, but will have minor procedural differences, which won't change the structure of the underlying database. Should I use one database per business unit, or one big database for all the units? The business units are totally separate
My preference is for one database per client. The advantages:
if a client gets too big, they're easy to move - backup, restore, change the connection string, boom. Try doing that when their data is mixed in with others in a massive database. Even if you use schemas and filegroups to segregate, moving them is not a cakewalk.
ditto for deleting a client's data when they move on.
by definition you're keeping each client's data separate. This is often going to be a want, and sometimes a need. Sometimes it will even be legally binding.
all of your code within a database is simpler - it doesn't have to include the client's schema (which can't be parameterized) and your tables don't have to be littered with an extra column indicating the client.
A lot of people will claim that managing 200 or 500 databases is a lot harder than managing 10 databases. It's not really any different, in my experience. You build scripts that automate things, you stagger index maintenance and backup jobs, etc.
The potential disadvantages are when you get up into the realm of 4-digit and higher databases per instance, where you want to start thinking about having multiple servers (the threshold really depends on the workload and the hardware, so I'm just picking a number). If you build the system right, adding a second server and putting new databases there should be quite simple. Again, the app should be aware of each client's connection string, and all you're doing by using different servers is changing the instance the connection string points to.
Some questions over on dba.SE you should look at. They're not all about SQL Server, but many of the concepts and challenges are universal:
https://dba.stackexchange.com/questions/16745/handling-growing-number-of-tenants-in-multi-tenant-database-architecture
https://dba.stackexchange.com/questions/5071/what-are-the-performance-implications-of-running-multiple-smaller-dbs-instead-of
https://dba.stackexchange.com/questions/7924/one-big-database-vs-several-smaller-ones
Your question is a design question. In order to answer it, you need to understand the requirements of the system that you want to build. From a technical perspective, SQL Server -- or really any database -- can handle either scenario.
Here are some things to think about.
The first question is how separate your clients need the data to be. Mixing data together from different business units may not be legal in some cases (say, the investment side of a bank and the market analysis side). In such situations, separate databases are the solution.
The next question is security. In some situations, clients might be very uncomfortable knowing that their data is intermixed with other clients data. A small slip-up, and confidential information is inadvertently shared. This is probably not an issue for different business units in the same company.
Do you have to deal with different uptime requirements, upload requirements, customizations, and perhaps interaction with other tools? If one business unit will need customizations ASAP that other business units are not interested in, then that suggests different databases.
Another consideration is performance. Does this application use a lot of expensive resources? If so, being able to partition the application on different databases -- and potentially different servers -- may be highly desirable.
On the other hand, if much of the data is shared, and the repository is really a central repository with the same underlying functionality, then one database is a good choice.
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'm creating a multi-user/company web application in PHP & MySQL. I'm interested to know what the best practice is with regards to structuring my database(s).
There will be hundreds of companies and thousands of users of this web app so this needs to be robust. Each company won't be able to see other companies data, just their own. We will be storing mainly text data and will probably only be a few MB per company.
Currently the database contains 14 tables (for one sample company).
Is it better to put the data for all companies and their users in a single database and create a unique companyID for each one?
or:
Is it better to put each company's data in its own database and create a new database and table set for each new company that I add?
What are the pluses and minuses to each approach?
Thanks,
Stephen
If a single web app is being used by all the different companies, unless you have a very specific need or reason to use separate databases (it doesn't sound like you do), then you should definitely use a single database.
Your application will be responsible for only showing the correct information to the correct authenticated users.
Multiple databases would be a nightmare to maintain. For each new company you'd have to create and administer each one. If you make a change to one schema, you'll have to do it to your 14+.
Thousands of users and thousands of apps shouldn't pose a problem at all as long as you're using something that is a real database and not Access or something silly like that.
Multi-tenant
Pluses
Relatively easy to develop: only change database code in one place.
Lets you easily create queries which use data for multiple tenants.
Straightforward to add new tenants: no code needs to change.
Transforming a multi-tenant to a single-tenant setup is easy, should you need to change your design.
Minuses
Risk of data leak between tenants if coding is sloppy. Tenant view filters can in some cases be employed to reduce this risk. This method is based on using different database user accounts for different tenants.
If you break the code, all tenants will be affected.
Single-tenant
Pluses
If you have very different requirements for different tenants, several different database models can be beneficial. This is the best case for using a single tenant setup.
If you code sloppily, there's practically no risk of data leak between tenants (tenant A will not be able to access tenant B's data). In addition, if you accidentally destroy the schema of one tenant through a botched update, other tenants will remain unaffected.
Less SQL code when you don't need to take tenant ID values into account in your queries
Minuses
Database schemas tend to differentiate with time, often resulting in a nightmare. Using a database compare tool, you can alleviate this problem, but potentially many schemas need to be compared.
Including data from several databases in one query is typically complex, and often requires prepared statements.
Developing is hard, since you need to make the same changes to multiple schemas.
The same database entity can appear in many databases with different ID keys, resulting in confusion.
Transforming a single-tenant to a multi-tenant setup is very hard, should you need to change your design.
A single database is the relational way. One aspect from this perspective is that databases gather statistics about database usage and make heavy use of this. If you split things up you will be shooting yourself in the foot as the statistics will be fragmented.