MySQL doesn't have transactions for DDL (i.e. alter table ), which Postgres does. This is very handy for migrations, as you can modify columns and update data in the same transaction and rollback if things go awry.

MySQL has lots of features, which don't work in specific cases you will likely encounter some day. This is the case very frequently (and of course this is also the case with transactions). If nothing quite works as you expect, I'd say it falls in the category of a "newb trap". Maybe it would behove us to pick the options that have the lowest amount of those.