If you are upgrading to SQL Server 2005, pay attention to this one ...
SQL Server has long supported two forms of OUTER JOIN syntax, the ANSI syntax (using LEFT OUTER JOIN, RIGHT OUTER JOIN, etc.), and the simplified T-SQL syntax (using *= and =*). If you've always used ANSI syntax then you are safe, but if you have any existing code that uses the simplified T-SQL syntax, that code will not run on SQL Server 2005, and the following error message will be returned:
The query uses non-ANSI outer join operators ("*=" or "=*"). To run this query without modification, please set the compatibility level for current database to 80 or lower, using stored procedure sp_dbcmptlevel. It is strongly recommended to rewrite the query using ANSI outer join operators (LEFT OUTER JOIN, RIGHT OUTER JOIN). In the future versions of SQL Server, non-ANSI join operators will not be supported even in backward-compatibility modes.
Fortunately, that message also provides the solution. Using the sp_dbcmptlevel stored procedure you set the backwards compatibility level so that the old style outer joins work. Until you manually fix them all, that is.