Along with SQL Server 2012, Microsoft also released a new set of SQL Server 2012 Express editions. SQL Server Express is a free edition of SQL Server, and it’s used as the internal database for hundreds of third-party products.
Related: SQL Server 2012 Editions
Although it's free, however, it also has several limitations. Compute-wise, the new SQL Server 2012 Express editions are limited to the lesser of one socket or four cores. The editions are also limited in size. The maximum memory for the database engine is limited to 1GB and the maximum relational database size is 10GB.
Although SQL Server Express is limited in scalability, a common misconception is that it’s limited to a single database or 10 connections. Neither of these is true. SQL Server Express can support multiple databases where each database can be up to 10GB. The myth about the number of connections is probably a holdover from the early days of MDSE (Microsoft Database Engine—the first version of the desktop SQL Server Engine that was released in the SQL Server 2000 timeframe.)
SQL Server 2012 Express has no limits on incoming connections or workload other than the CPU and memory limitations. And it comes in both 32-bit and 64-bit versions. You can download all of the SQL Server 2012 Express editions from Microsoft’s website.
SQL Server Express (Database Only)
The basic offering of SQL Server 2012 Express, SQL Server Express (Database Only) edition includes only the relational database engine. Like the more full-featured editions of SQL Server, it runs as a service. This edition is the best choice when you need to bundle database services with your application. It’s fully capable of supporting production applications for small-to-midsized businesses (SMBs).
SQL Server Express with Tools
The SQL Server Express with Tools edition includes the basic relational database as well as the SQL Server Management Studio Express (SSMSE). SSMSE enables you to manage your SQL Server Express instances and databases. You can also download SSMSE separately if you later need it to manage the Database Only edition. This edition is the best choice when you’re internally developing several of your own applications, and you need to manage multiple databases.
SQL Server Express with Advanced Services
This is the most full-featured version of SQL Server 2012 Express. It includes SSMSE, SQL Server Data Tools (SSDT), full-text search, and the Reporting Services subsystem. The Reporting Services implementation in SQL Server Express with Advanced Services is limited to 4GB and can access only the local instance. This edition is the best choice when you’re developing your own custom applications, and you need reporting as well as database services.
SQL Server Express LocalDB
SQL Server Express LocalDB is a new option with the SQL Server 2012 release. Unlike the other versions of SQL Server Express, LocalDB runs in user mode—not as a service. LocalDB is for developers and is primarily intended to help you test code for your deployments. This edition uses the same sqlservr.exe program as the other versions and is 100 percent code compatible with the other editions of SQL Server. LocalDB has a zero configuration installation.
Learn more: Microsoft SQL Server 2012 Licensing Options