SQL Server Compact
| Filename extension | .sdf |
|---|---|
| Developed by | Microsoft |
| Type of format | Relational database |
Microsoft SQL Server Compact (SQL CE) is a compact relational database produced by Microsoft for applications that run on mobile devices and desktops. Prior to the introduction of the desktop platform, it was known as SQL Server for Windows CE and SQL Server Mobile Edition. The latest release is the SQL Server Compact 4.0 supporting .NET Framework 4.0, and dropping support for Windows Mobile in this release. It includes both 32-bit and 64-bit native support. SQL CE targets occasionally connected applications and applications with an embedded database. It is free to download and redistribute. An ODBC driver for SQL CE does not exist, nor is one planned. Native applications may use SQL CE via OLE DB.
SQL Server Compact shares a common API with the other Microsoft SQL Server editions. It also includes ADO.NET providers for data access using ADO.NET APIs, and built-in synchronization capabilities, as well as support for LINQ and Entity Framework. Future releases will unify the synchronization capabilities with Microsoft Synchronization Services. Unlike other editions of Microsoft SQL Server, SQL CE runs in-process with the application which is hosting it. It has a disk footprint of less than 2 MB and a memory footprint of approximately 5 MB. SQL CE is optimized for an architecture where all applications share the same memory pool.Windows Store apps for Windows 8 cannot use SQL Server Compact edition, or any other edition of SQL Server.
SQL CE databases can support ACID-compliance, but do not meet the durability requirement by default because AutoFlush buffers changes in memory (including enlisted ambient transactions and explicit SQL CE transactions that do not override the Commit() call with an CommitMode.Immediate value). Therefore, committed transaction changes can be lost. To meet the durability requirement the commit call on the transaction must specify the immediate flag. Like Microsoft SQL Server, SQL CE supports transactions, referential integrity constraints, locking as well as multiple connections to the database store. However, nested transactions are not supported, even though parallel transactions (on different tables) are. The current release does not support stored procedures or native XML data type either. It uses a subset of T-SQL for querying and due to lack of XML support, XQuery is not supported either. Queries are processed by an optimizing query processor. SQL CE databases also support indexing, as well as support remote data replication (local caching of data in remote databases) and merge replication (bidirectional synchronization with master databases).
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