[HelloNurse]

"Splitting" a table usually means creating two new ones and dropping the old one after migrating its content with a complex migration script followed by thorough testing. Dropping columns is not only abnormal (adding columns is far more common: features tent to be added, not removed, over time) but also a very crude tool.

[calpaterson]

Well what I meant was: when you break one table out of another. The kind of thing that comes up when you learn that there's a one-to-many in the domain that you didn't know about when you started.