Microsoft SQL Server (MS SQL) is a widely used database server. For an overview of its history and versions, see https://en.wikipedia.org/wiki/Microsoft_SQL_Server#History.
This conversion guide is meant, first, to help users evaluate whether the process should be performed at all. It then goes on to detail how this can be done, adding bits of experience collected by different people.
There are two important things to take into account when migrating. First, moving the data from one database server to another can be trivial or not, depending on your database schema. There are many tools to help you with this process. The standard data conversions are listed in this document.
Second, you will need to migrate any stored procedures and triggers manually. This is the tricky part. There are many differences, some minor, some important; this document attempts to address most of them, giving examples on the most frequent problems and how to solve them.
Warning: This guide was written in 2003, when Firebird 1.0 was the current version. Although it has been updated in a few places, the document as a whole still awaits a thorough revision. That shouldn't stop you from using it - just be aware that some of the content is outdated, and do read the Release Notes of any Firebird versions greater than 1.0 up to and including your own version.