SQL Server Editions
Last updated May 26, 2005.

If SQL Server has an Achilles heel, it's that it only runs on Microsoft operating systems. Oracle and IBM's DB2 have a larger spread of the operating system market, since they run on various flavors of UNIX and other big-iron operating systems. Even so, SQL Server runs on every OS that Microsoft makes—from the handheld CE devices to the big multiprocessor clusters.
Although it may not be apparent at first glance, it's important to know about the various editions of SQL Server. There are limitations and advantages to each, and the various editions run on different Microsoft operating systems. I'll present a quick rundown of each edition, and then show a table that gives the requirements and minimums. I've ordered these editions by what I think you'll encounter most often in the field—although that's just a judgment call on my part. Depending on what your shop does, you may see multiples of these editions, so it's important to know what you're dealing with.
At the core of all these editions are the file structures and command sets of Transact-SQL (T-SQL). Microsoft made sure that the file types are the same (with some limitations) between editions. What this means is that a database created on SQL Server Personal Edition running on Windows 98 can be accessed, restored, transferred, and programmed just like one running on a 32-processor cluster. It's typically easier to go up in editions than down, and that holds true for SQL Server as well. Some constructs just don't map well between them, such as a clustered multifile-gigabyte database that you want to use on your CE device, but there are ways that they can share data.
Let's look at what each of the SQL editions offers.
Standard Edition
About 80% of the systems I've seen run the Standard Edition of SQL Server. This edition supports from one to four processors and 2GB of RAM, which is in the right ballpark for a lot of departmental implementations. The Standard Edition provides all the features that SQL Server is famous for, such as:
•	Data Transformation Services (DTS), which provides import, export, and transformations of data between various sources
•	Replication between other Microsoft SQL Servers and other vendors
•	English Query
•	XML support
•	Full-text searches
In short, this edition provides most of what you need for departmental or small-business implementations.
There are some limitations; you don't get clustering ability or some of the advanced features for OLAP. This is the right version for a larger shop that needs high availability and advanced SQL features such as indexed views.
This version installs only on Windows 2000 Server or higher.
Personal Edition
The Personal Edition of SQL Server has the same features as the Standard Edition. Its primary constraints are the licensing and operating-system limitations.
The Personal Edition won't use more than two processors, and has a query governor that will impact performance if you push it hard. It also won't do transactional replication, but it can be a subscriber to that kind of replication.
This version can be installed on Windows 98 and higher. You get full-text search and SQL Server 2000 Analysis Services with Personal Edition, but it can't be installed on Windows 98 or Windows ME. The other issue with these operating systems is that they don't have services, so certain functions such as the SQL Agent can't run when you're not logged on.
MSDE
The Microsoft Data Engine (MSDE) is another widely used edition of SQL Server. It ships with the Visual Studio Development tools, you can get it stand-alone, and it even comes on the Office Professional CD. MSDE replaces JET as the distribution engine of choice for distributed applications.
It has the same basic features as SQL Server Standard Edition, and is a great way to develop and create applications that can be migrated to other SQL Server editions. You can back up a database on MSDE and restore it to an Enterprise Edition of SQL Server with no changes.
Many web servers use this edition of SQL Server because the distribution is royalty-free. In other words, if you develop an application with the products listed below, you can provide the MSDE install along with your product, and not have to pay Microsoft a fee. (That assumes, of course, that you purchased the development tools to begin with, and this is always subject to change as Microsoft evolves its licensing.) These are the tools:
•	SQL Server 2000 (Developer, Standard, and Enterprise Editions)
•	Visual Studio .NET (Architect, Developer, and Professional Editions)
•	ASP.NET Web Matrix Tool
•	Office XP Developer Edition
•	MSDN Universal and Enterprise subscriptions
You can use MSDE with Microsoft Access, but you can't give it away for free with your Microsoft Access applications.
There are two major limitations to MSDE:
•	A query-governor is built in, to limit the performance of applications of greater than five threads or around five users, depending on how your application is written. It also has no graphical tools or online books installed with it, which means that you'll have to write code to manage it. There are sites on the web that provide free or inexpensive tools to manage MSDE, however.
•	You're limited to databases less than 2GB, but that really isn't so bad considering the cost. SQL Mail can't be used with MSDE.
You can use MSDE in SQL Server replication, but if you connect to a full edition of SQL Server you'll need to license (with a Client Access License, or CAL) the MSDE machine to be a client to that server. You'll also usually want to set up MSDE to be a subscriber or publisher of data, but not a distributor—it's just not powerful enough to do serious levels of replication.
If you're looking for a quick, easy way to jump into SQL Server or set up a web database, MSDE is a great way to go.
Enterprise Edition
The Enterprise Edition is the big-iron edition of SQL Server. It has everything that all the other editions have—and more. I'll cover the features in a moment. In addition to those features, Enterprise Edition boasts better performance than the other editions, and can use up to 32 processors and 64GB of RAM. You'll get better parallelism of queries, meaning that the server uses the symmetric multiprocessors to chunk up the queries to run at the same time.
In addition to the performance gains, the other advantage with this edition is its scalability. By pairing it with Windows 2000 Advanced Server, you can cluster SQL Server Enterprise to failover to another system for production-level uptime. Data on SQL Server Enterprise can be carved up to work in parallel, called scaling out. Another way to provide higher uptime using this version is log shipping, meaning that changes made on one server can automatically be transferred to another server (perhaps located elsewhere) and applied to keep them in periodic sync.
As far as the enhanced features go, you'll get advanced analysis with Enterprise Edition. You can define OLAP partitions and create larger cubes. To store these increased amounts of data, you often need a type of storage called ROLAP, and this edition handles that better than its smaller siblings. If you need almost real-time OLAP, this is the edition for you.
Another feature that this edition provides that's often overlooked is as a back-end to reporting data. When you structure reporting data, it often has a negative impact on performance. With SQL Server Enterprise Edition, you get indexed views, which can really help a skilled developer speed up those reports.
There's yet another benefit to this edition: The samples area is greatly enhanced in this release. For the developer, this sample code can be very useful.
As you might guess, you need a bit more horsepower to run this version.
Developer Edition
With the Developer Edition, you can develop applications for SQL Server. You get all the features of the Enterprise Edition, but with a development license that prohibits you from deploying this edition in production. It installs on Windows 2000 Professional and higher.
With this edition, you have the right to install SQL Server 2000 Windows CE Edition and deploy those apps royalty-free, although the CE devices have to license the CE version.
The other beauty of this edition is that it can be upgraded for production use to SQL Server 2000 Standard or Enterprise Edition.
Evaluation Editions
The Evaluation editions are just that—the full-up featured editions (Standard and Enterprise) that stop working after about 120 days. They don't cost anything, but you can't legally use them in production or even development. They're to be used strictly for deciding whether to buy the product.
CE Edition
The CE Edition of Microsoft SQL Server has the same tools and SQL syntax that the developers use for full-fledged SQL Server applications. It's the only relational database that runs on a pocket device. The primary use you'll see for this edition is to act as a merge-replication platform for distributed applications. It does this with HTTP, and even supports encryption. You have to run CE 2.11 or later to run the program, and you can use databases to 2GB—not that you see many CE devices sporting 2GB of RAM these days!
MSDN
If you're a member of the Microsoft Developer Network (MSDN), there are repeats of each of the editions in your subscription. The primary differences are the licensing (you can't deploy it for production) and the fact that some of the editions are "checked builds," meaning that they can display more debug information as they work. These debug editions are much slower than the standard released code.