The best Source Code Control System for SQL Server is written in SQL

Super Database Compare: The Best Source Code Control System for SQL Server
is written entirely in SQL and runs in the browser . . .

forget about that:

The best source control system for SQL Server needs to be able to compare Production databases to Development, and Development Databases to incremental builds and previous versions, regardless of weather the target SQL Servers are on the same network or anywhere else in the world. And it needs to be able to do that fast, with a single click. With Super Databse Compare for SQL Server:

You can compare the schemas of any two SQL Server databases,
Located on any SQL Server 20XX Servers anywhere in the world.
You can drill down and find any procedures that are different...
You can drill down further and see the differences in the code staggered side by side.
You can find all of the column and attribute differences with a single click.
Analyze by Views, Tables, Procedures, Functions or Keys.
MySQL version included; a similar Relational App that compares MySQL Databases.

In the screenshots, the Developer has compared the Stored Procedures collections between the Production and Development version of an Enterprise Database; they've drilled in to see which procedures are different or missing between the servers and then drilled in again to see the individual breaks in the lines of code in one of the different procedures.

SQL Server 2000/2005/2008, SQL Server, and Microsoft are registered trademarks of Microsoft Corporation. Transact-SQL is a trademark of Sybase, Inc. The Relational Framework, Super Database Compare and the SchemaSpider IDE for SQL Server are © 2004,2007,2010 RelationalFramework.com.