Answers for "modify column sql not null"

change sql column from null to not null

ALTER TABLE [TABLE_NAME] CHANGE [COLUMN_NAME] [COLUMN_NAME] [COLUMN_TYPE] NOT NULL DEFAULT [DEFAULT];

alter column to not null with default value sql server

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.