Introduction
It gives me great pleasure to introduce a new version of SQL Express called SQL Express LocalDB.
LocalDB is created specifically for developers. It is very easy to install and requires no management, yet it offers the same T-SQL language, programming surface and client-side providers as the regular SQL Server Express. In effect the developers that target SQL Server no longer have to install and manage a full instance of SQL Server Express on their laptops and other development machines. Moreover, if the simplicity (and limitations) of LocalDB fit the needs of the target application environment, developers can continue using it in production, as LocalDB makes a pretty good embedded database too.
Background
Before focusing on technical description of LocalDB, I’d like to provide some background on the direction we took building it.
Today SQL Server Express serves two distinct needs. On one hand it is a free edition of SQL Server. The installation, management and programming of SQL Express in this role is expected to be 100% compatible with other editions. It can be used for learning, training and to run relatively small production database (with less than 10GB of data). Upgrade from SQL Express to paid SQL Server editions is a matter of typing in a license key and no installation is required.
But SQL Express is also SQL Server edition for developers writing applications targeting SQL Server. In this role the programming of SQL Express is still expected to be 100% compatible with other SQL Server editions, but SQL Express is supposed to be small, simple, low-footprint, require no configuration or administration, run as non-admin user, etc.
Our approach so far was to try to make SQL Express perform well in both roles. But as SQL Server product matured, and in effect added more complexity, it became harder and harder for SQL Express to be both compatible with other SQL Server editions and small/simple. The challenge is most visible in installation and configuration of SQL Express. In SQL Server "Denali" we decided to change the approach it and introduce a dedicated version of SQL Express for developers – LocalDB that delivers the simplicity and yet is compatible with other editions of SQL Server at the API level.
Also, by making LocalDB a better SQL Express for developers, we hope to be able to improve the regular SQL Express to be a better free SQL Server. We’d be very happy to hear your feedback in this area, especially if you’re using SQL Express as a database server and find any issues caused by the new features that were introduced to fit the needs of developers and desktop environment.
Source: http://blogs.msdn.com/b/sqlexpress/archive/2011/07/12/introducing-localdb-a-better-sql-express.aspx
