>
> Is there a way to change a blob field from sub_type 1 to sub_type 0
> without losing the data in the column? I have tried alter table alter
> column but the engine is not letting me change it. Perhaps I can
> modify some system tables?
>
>

don't do a system table mod
create a new field, update the new from old then drop the old.
If you want the same name, then do it again with the original field name
ALan