change_column

I know this might seem basic, but I did not know that for many of the operations change_column will retain the data in the column.

Here are some of the thing change_column can do without loosing data:

• changing or setting default values
• changing the name of the column
• you can even change the column data type for certain data type mappings

Remember that it might make a difference as to which db you're using. I did my tests on a sqlite3 db.