We've rolled our own variant of this, which uses an XML file as input. Just easier to parse than SQL schema definitions. The tool compares the schema defined by the XML with the DB, and applies changes as needed.

We used Sybase SQLAnywhere, and a complication there was that if you had materialized views against a table, you had to drop and recreate that view when adding or removing columns in the table. And when you recreate it, you of course have to remember to recreate the indexes on that materialized view.

Tracking this in case you have multiple materialized views touching multiple tables became a bit tricky, and you don't want to do the "dumb" thing to just always drop and recreate, or per-column, since some of them might take an hour or so to recreate and reindex.

The tool has some built-in safeties like never dropping columns if it's missing (have to add explicit element for that in the XML), and only performs safe column definition changes, ie integer to varchar(50) is safe, integer to varchar(3) is not, etc.

It really made database migrations very painless for us, great since we've have hundreds of on-premise installations. Just modify the XML, and let the tool do its job.

And since its our tool, we can add functionality when we need to.