Comparison Tool for MySQL data base schemas We'd like to update an old database schema for a new software release that requires changes in database schema (additional colums, column renames, table renames, datatypes, ...). Is there any comparison tool for MySQL data base that can help to adapt the old schema to the new one without the loss of any stored data where possible? (free software preferred)

The changes can be made by hand, yes. But we're looking for a more comfortable way and to catch all the changes made.
This isn't the a very sexy answer but mysqldump &amp; sdiff.

mysqldump -u root -p --no-data -h oldHost databases db1 db2 db3 &gt; /tmp/old.sql
mysqldump -u root -p --no-data -h newHost databases db1 db2 db3 &gt; /tmp/new.sql
sdiff /tmp/old.sql /tmp/new.sql


sdiff will give you a side by side comparison with differences paired w/ a > or &lt; indicator.  I've found this to be useful in the exact scenario you describe.

The example supposes you have the new schema initialized on a different host, but this certainly isn't a requirement.  It could be a different instance (e.g. port) on the same host or the same instance with different database names.