Microsoft makes SQL Server available in multiple editions, with different feature sets and targeting different users. These editions are:
SQL Server Compact Edition (SQL CE)
The compact edition is an embedded database engine. Unlike the other editions of SQL Server, the SQL CE engine is based on SQL Mobile (initially designed for use with hand-held devices) and does not share the same binaries. Due to its small size (1MB DLL footprint), it has a markedly reduced feature set compared to the other editions. For example, it supports a subset of the standard data types, does not support stored procedures or Views or multiple-statement batches (among other limitations). It is limited to 4GB maximum database size and cannot be run as a Windows service, Compact Edition must be hosted by the application using it. The 3.5 version includes considerable work that supports ADO.NET Synchronization Services.
SQL Server Developer Edition
SQL Server Developer Edition includes the same features as SQL Server Enterprise Edition, but is limited by the license to be only used as a development and test system, and not as production server. This edition is available to download by students free of charge as a part of Microsoft's DreamSpark program.
SQL Server 2005 Embedded Edition (SSEE)
SQL Server 2005 Embedded Edition is a specially configured named instance of the SQL Server Express database engine which can be accessed only by certain Windows Services.
SQL Server Enterprise Edition
SQL Server Enterprise Edition is the full-featured edition of SQL Server, including both the core database engine and add-on services, while including a range of tools for creating and managing a SQL Server cluster.
SQL Server Evaluation Edition
SQL Server Evaluation Edition, also known as the Trial Edition, has all the features of the Enterprise Edition, but is limited to 180 days, after which the tools will continue to run, but the server services will stop.
SQL Server Express Edition
SQL Server Express Edition is a scaled down, free edition of SQL Server, which includes the core database engine. While there are no limitations on the number of databases or users supported, it is limited to using one processor, 1 GB memory and 4 GB database files. The entire database is stored in a single .mdf file, and thus making it suitable for XCOPY deployment. It is intended as a replacement for MSDE. Two additional editions provide a superset of features not in the original Express Edition. The first is SQL Server Express with Tools, which includes SQL Server Management Studio Basic. SQL Server Express with Advanced Services adds full-text search capability and reporting services.
SQL Server Fast Track
SQL Server Fast Track is specifically for enterprise-scale data warehousing storage and business intelligence processing, and runs on reference-architecture hardware that is optimized for Fast Track.
SQL Server Standard Edition
SQL Server Standard edition includes the core database engine, along with the stand-alone services. It differs from Enterprise edition in that it supports fewer active instances (number of nodes in a cluster) and does not include some high-availability functions such as hot-add memory (allowing memory to be added while the server is still running), and parallel indexes.
SQL Server Web Edition
SQL Server Web Edition is a low-TCO option for Web hosting.
SQL Server Workgroup Edition
SQL Server Workgroup Edition includes the core database functionality but does not include the additional services.