SQL CE

Microsoft SQL Server Compact or SQL CE is an embedded relational database intended for use both on mobile devices and desktops. SQL Compact shares a common programming interface with other SQL Server editions, making it easy to use for .NET developers familiar with standard SQL Server.

There are many limitations compared to a standard SQL Server instance, but that’s expected for a small embedded database engine. You can’t write stored procedures, for example - but one of the main purposes of stored procedures is to avoid frequent network round-trips to the server. With embedded databases, stored procedures have less appeal. Also, XML data type is not supported in SQL Compact.

SQL Server Compact holds its databases in a single file with the .SDF extension. However, that extension is just a recommendation, so any extension can be used for the database file. SDF files can be compressed and encrypted. If a database is created with a password specified, it will be encrypted and will never allow access without the correct password.

Some of the well-known competitors to SQL Server Compact are SQLite and Pervasive PSQL, which run on many more platforms compared to SQL CE.