LocalDB

When developing applications that use SQL Server for persistence, you now have 3 options:

1. Install a full version of SQL Server.
2. Install SQL Server Express.
3. Use LocalDB.

Option 1 is expensive, and has a big footprint.

Option 2 is free, is limited, and has a big footprint.

Option 3 is free, is limited, and has a small footprint.

LocalDB seems to be the preferred way for developers to connect to databases while in the development process.  It is installed with Visual Studio 2012 forward.  Any databases created require no administration or configuration.

To connect to you LocalDB instance, simply use (localdb)\v11.0.  Databases, tables, and stored procedues can all be created in Visual Studio, so there is no need to install SQL Server at all while developing or doing research.