SSDT gets you most of the way but not all the way there. It can rebuild a table by copying the rows if you're changing things that are evident from a diff of th

SSDT gets you most of the way but not all the way there. It can rebuild a table by copying the rows if you're changing things that are evident from a diff of the production schema against your desired state, if it's not possible with ALTER TABLE. But for complicated arbitrary transformations, it does make you use a trapdoor where you write a migration script that gets executed after the desired state is applied. In practice, we consciously avoid doing this, but we are perhaps making sacrifices for the tool's limitations. I've occasionally done hacks like creating a new table with the desired new shape, then creating a view that converts the old data to the new format and merges it with the new data. SSDT is capable of deploying that, but it's not the greatest situation.