Microsoft provides 2 primary editions for SQL Server: Standard and Enterprise. Standard edition provides basic SQL Server features and will serve the needs of most businesses. Enterprise edition offers additional functionality and a much heftier price tag.

Which Edition Do I Choose?

Assume you need SQL Server Standard unless you fall into any of these categories:

You are working with large volumes of data.

Working with terabyte-class databases or billion-row tables? You should choose Enterprise edition. Enterprise offers table partitioning, parallel indexing, and indexed views that can significantly improve performance in large environments.

You are working in a high-availability, mission-critical environment.

If you're working in a 24/7/365 environment, you probably need Enterprise. Online indexing will allow you to maintain indexes without scheduling down-time, and Online Restore and Fast Recovery are both options you want when recovering from a failure.

You are working with a large Business Intelligence data warehouse.

SQL Server Reporting Services (SSRS) is available in both Standard and Enterprise editions of SQL Server. However, Enterprise edition offers substantially more BI features, such as parallel processing, cube partitioning, and text mining.

You need to replicate data from Oracle.

Enterprise is the only edition that allows you to replicate data from Oracle.

You have a limited budget.

SQL Server Standard is significantly less expensive than Enterprise when licensed per cpu.

If you do not fall into any of these categories, then Standard edition will most likely suffice.

Myths

Standard isn't as stable as Enterprise.

Not true. Standard and Enterprise both use the same core; the only difference is the additional features that Enterprise provides.

My other database servers are Enterprise, so all of my new servers need to be Enterprise, too.

Not true. While having a homogeneous environment does simplify many things (planning, maintenance, etc.), you can easily mix and match SQL Server editions within an environment to best meet your needs (and budget!).

I need Enterprise edition in order to replicate partitioned tables.

Not true. Replication can exist between partitioned and non-partitioned tables. In fact, replication by default does not create partitioning schemas on the subscription database, so the destination table is not partitioned unless explicitly requested. That said, if the source tables are partitioned, there may be good cause for the destination tables to be partitioned too, and Enterprise edition should be seriously considered.

I need Enterprise edition in order to cluster.

Not true starting in SQL Server 2005. Both 2005 and 2008 Standard editions support 2 node clusters. In a lot of enterprises, you will see Enterprise installed for clustering only. If you have a two node active/passive cluster and that is your only reason: you are probably overpaying and could be fine with standard edition.

I need Enterprise edition to access more memory.

Not true with 2005 or 2008. These versions of SQL will address as much memory as the OS allows in Standard or Enterprise edition.

Additional Resources

To see a full comparison of features, visit Microsoft's product pages:

SQL Server 2005: http://www.microsoft.com/Sqlserver/2005/en/us/compare-features.aspx

SQL Server 2008: http://download.microsoft.com/download/2/D/F/2DF66C0C-FFF2-4F2E-B739-BF4581CEE533/SQLServer2008EnterpriseandStandardFeature%20Compare.pdf