Liquibase is a tool for maintaining database schemas in a platform-independent form. It can then generate platform-specific SQL for the database system(s) of your choice.
I introduced it at Misys to help my team escape the chaos we had got into. Even the simplest change meant changing eight files (creation and upgrade scripts for each of four DB platforms (Oracle, SQL Server, DB2 LUW and DB2 for System i). Then they all had to be tested. It was a nightmare.
Changing to Liquibase meant that any change involved changing one file. You still have to test all the platforms, of course, but Liquibase makes that easy too, as you can run the same script from your workstation, just changing a parameter or two to make it deal with each different platform.
All in all it’s a fine open-source project, which I would highly recommend if managing your schema is starting to look at all onerous.
And if you need help with it, drop me a line here at Tin Lion Software.