I don't think it was expected by many but after several years of strong link between SQL Server and Windows, impossible happened on March 7th, 2016 - Microsoft announced bringing SQL Server to Linux. It was not only announced, but a private preview was made available for testing. The preview proves that Microsoft really made some big steps to make it happen. Actually, those are not only steps, but the project is very advanced. Core relational database capabilities are already in the preview, availability features are going to be released in 2017.
SQL Server on Linux - why?
SQL Server is alread a very successful product. It is very popular and advanced. It is available as a service in Amazon AWS and in Azure. Discussions SQL Server vs Oracle are endless. Knowing that, we could ask why Microsoft decided to invest in porting it to Linux? Well. When I recall some of such discussions, necessity of having Windows Server was definitely one of the most important disadvantages of SQL Server. For some reasons, decision makers at IT companies always wanted to keep all options on the table. Choosing SQL Server instead of Oracle was perceived as limitation. If we proceed with Microsoft, we will always have to stay at Windows Server, they said. That is why I think porting SQL Server to Linux can eliminate this one reason for choosing Oracle.
Will Linux be a true choice?
Although, I am excited about the announcement, we have to remember that it does not automatically mean that there will be a true Linux option for production systems. It could be like Oracle RDBMS which can be installed on Linux or Windows but production installations are not recommended on Windows. The operating system from Microsoft is a good option but for developers not the real users.
Is there a risk that SQL Server will work on Linux but only with basic functionality or unreliably? Oh, yes. It is possible. We will see how it will evolve.
And now I encourage you to test the preview - www.microsoft.com/en-us/server-cloud/sql-server-on-linux.aspx.