Setting allow nulls by default to true changes the default null type of a column from not null to null, in compliance with the SQL standard. The Transact-SQL default value for a column is not null, meaning that null values are not allowed in a column unless null is specified in the create table or alter table column definition.
You cannot use allow nulls by default to change the nullibility of a column during select into statements. Instead, use convert() to specify the nullibility of the resulting columns.
