A real project usually have a lot of things that changes over time, including how to store the data. Adding columns and tables are basically the only simple thi

A real project usually have a lot of things that changes over time, including how to store the data. Adding columns and tables are basically the only simple things and not even new tables are always easy if they are connected to other tables and you have contraints that means they have to be pre-filled with something from the old database. Other things that can change is splitting one table into multiple table while keeping all data, splitting or joining columns while keeping data and so on. For large datasets this may cause headaches. Any error will also cause a lot of extra work.