Paul J said..
Some details on Microsoft SQL Server 2005 database editions
Enterprise Edition
Large organizations with complex requirements should take advantage of Enterprise Edition. It offers advanced enterprise data management, developer productivity, and business intelligence tools to meet the needs of critical applications. Significant advancements in high-availability technologies have been made, including new advanced database mirroring functionality such as log shipping, additional backup and restore capabilities, and replication enhancements to allow organizations to build and deploy highly reliable applications. Additionally, Enterprise Edition provides analytical and enterprise reporting capabilities to deliver business insights to all levels of your organization. Enterprise Edition delivers out-of-the-box robust scalability, high availability, and advanced business intelligence features, making it the most competitively priced and comprehensive enterprise solution available.
Standard Edition
Standard Edition is a complete data management and analysis platform designed for medium-sized businesses, departmental usage, and infrastructures that require highly available systems. Standard Edition has added 64-bit support and high-availability features such as clustering and database mirroring. Standard Edition offers enhanced business intelligence functionality and SQL Server Integration Services, SQL Server Analysis Services, and SQL Server Reporting Services.
Workgroup Edition
Workgroup Edition is specifically for small- to medium-sized organizations. It provides a fast, easy-to-use, and affordable database solution. It has no limits on database size or connections for handling departmental and branch location needs. Integrated with Visual Studio® and the Microsoft .NET development framework, Workgroup Edition allows you to quickly develop dynamic, robust, integrated applications. It is the ideal choice for organizations that require an easy-to-manage, reliable, and robust solution with more scalability than the SQL Server Desktop Engine (MSDE) or SQL Server 2005 Express.
Express Edition
Express Edition is a no-cost, redistributable version of the SQL Server 2005 database engine. This edition provides the fastest way for novice developers to learn to develop and deploy small-footprint data-driven applications. It is also useful to larger enterprise companies that want to dedicate smaller databases to developer projects. Express Edition is tightly integrated with the SQL Server 2005 Reporting Services controls that are included in Visual Studio 2005, allowing developers to easily create sophisticated reports that include tables, charts, and graphics. Express is an easy way for customers and partners to get started with SQL Server 2005. Partners can even embed and redistribute Express Edition with their applications.