LocalDB is new for Microsoft SQL Server 2012. It is an easy-to-install version of Express that requires no management, while offering the same T-SQL language, programming features and client-side providers (ADO.NET, ODBC etc) as regular Express. LocalDB uses the same
sqlservr.exe as SQL Server Express and other editions of SQL Server.
LocalDB avoids the need to install and manage a full instance of Express, and can also be suitable for use as an embedded database. LocalDB is managed using the SqlLocalDB utility. LocalDB replaces the SQL Server Express user instance feature which is now deprecated. LocalDB connections support the AttachDbFileName property, which allows developers to specify a database file location. LocalDB will attach the specified database file and the connection will be made to it.
Once LocalDB is installed on a machine, multiple applications can start multiple LocalDB processes, all started from the same
sqlservr.exe executable file from the same disk location. LocalDB does not create any database services; LocalDB processes are started and stopped automatically when needed.
The application connects using a connection string like "Data Source=(localdb)\v11.0" and the LocalDB process starts as a child process of the application. A few minutes after the last connection to this process is closed the process shuts down.