When using development tools to modify a schema, you can end up having applied a number of changes which cannot be applied without data loss using schema differencing and which need to be included in a migration script.

It would be helpful if there was some form of SQL trace which could monitor schema changes actually applied, and be used to generate a composite migration script.

If I use Enterprise manager, or Red Gate to refactor the schema, it is up to me to remember to save the generated SQL and any other SQL I might write along the way and compose a migration script.

I imagine this works well if you have very formal and proscriptive schema development procedures, but if you have a more exploratory style, you may find you have applied a set of changes that you no longer have the scripts for and can only do schema differencing to get from old to new.

If the DB statement execution was tracked, you could record all queries which had schema or data side effects and then have a simple of (complex) process to generate an amalgamated/derived script to do a proper migration of old to new.