Below is some information on the up coming release of SQL CE 4.0.
Introducing SQL Server Compact Edition 4
SQL CE is a free, embedded, database engine that enables easy database storage. We will be releasing the first public beta of SQL CE Version 4 very shortly. Version 4 has been designed and tested to work within ASP.NET Web applications.
Works with Existing Data APIs
SQL CE works with existing .NET-based data APIs, and supports a SQL Server compatible query syntax. This means you can use existing data APIs like ADO.NET, as well as use higher-level ORMs like Entity Framework and NHibernate with SQL CE. Pretty much any existing data API that supports the ADO.NET provider model will work with it.
This enables you to use the same data programming skills and data APIs you know today.
No Database Installation Required
SQL CE does not require you to run a setup or install a database server in order to use it. You can now simply copy the SQL CE binaries into the \bin directory of your ASP.NET application, and then your web application can run and use it as a database engine. No setup or extra security permissions are required for it to run. You do not need to have an administrator account on the machine. It just works.
Applications you build can redistribute SQL CE as part of them. Just copy your web application onto any server and it will work.
Database Files are Stored on Disk
SQL CE stores databases as files on disk (within files with a .sdf file extension). You can store SQL CE database files within the \App_Data folder of your ASP.NET Web application - they do not need to be registered in order to use them within your application.
The SQL CE database engine then runs in-memory within your application. When your application shuts down the database is automatically unloaded.
Shared Web Hosting Scenarios Are Now Supported with SQL CE 4
SQL CE 4 can now run in “medium trust” ASP.NET 4 web hosting scenarios – without a hoster having to install anything. Hosters do not need to install SQL CE or do anything to their servers to enable it.
This means you can build an ASP.NET Web application that contains your code, content, and now also a SQL CE database engine and database files – all contained underneath your application directory. You can now deploy an application like this simply by using FTP to copy it up to an inexpensive shared web hosting account – no extra database deployment step or hoster installation required.
SQL CE will then run within your application at the remote host. Because it runs in-memory and saves its files to disk you do not need to pay extra for a SQL Server database.
Visual Studio 2010 and Visual Web Developer 2010 Express Support
VS 2010 and Visual Web Developer 2010 Express will add SQL CE 4 tooling support for ASP.NET scenarios in an update we’ll be rolling out in the future. This will enable you to add SQL CE database files to your ASP.NET projects, use the Visual Studio Server Explorer to create and edit tables in them, and use higher-level designers like Entity Framework (see below) to model and map the database to classes that you can then query and program against using LINQ.
This means that in addition to using the same data APIs you know today, you will also be able to easily use the same development tools you already know with SQL CE.
Supports Both Development and Production
SQL CE can be used for both development scenarios and light-usage production usage scenarios. With the SQL CE 4 release we’ve done the engineering work to ensure that SQL CE won’t crash or deadlock when used in a multi-threaded server scenario (like ASP.NET). This is a big change from previous releases of SQL CE – which were designed for client-only scenarios and which explicitly blocked running in web-server environments. Starting with SQL CE 4 you can use it in a web-server as well.
There are no license restrictions with SQL CE.
Easy Migration to SQL Server
SQL CE is an embedded database – which makes it ideal for development and light-usage scenarios. For high-volume sites and applications you’ll probably want to migrate it to use SQL Server Express (which is free), SQL Server or SQL Azure. These servers enable much better scalability, more development features (including features like Stored Procedures – which aren’t supported with SQL CE), as well as more advanced data management capabilities.
We’ll ship migration tools that enable you to optionally take SQL CE databases and easily upgrade them to use SQL Server Express, SQL Server, or SQL Azure. You will not need to change your code when upgrading a SQL CE database to SQL Server or SQL Azure. Our goal is to enable you to be able to simply change the database connection string in your web.config file and have your application just work.
SQL CE 4 provides an easy, lightweight database option that you’ll now be able to use with ASP.NET applications. It will enable you to get started on projects quickly – without having to install a full database on your local development box. Because it is a compatible subset of the full SQL Server, you write code against it using the same data APIs (ADO.NET, Entity Framework, NHibernate, etc).
You will be able to easily deploy SQL CE based databases to a remote hosting account and use it to run light-usage sites and applications. As your site traffic grows you can then optionally upgrade the database to use SQL Server Express (which is free), SQL Server or SQL Azure – without having to change your code.