1. First Add Column In Table With Default Value Along With Constraint Name

ALTER TABLE Table_Name ADD Column_Name INT CONSTRAINT default_deleted DEFAULT(1)

NOTE : Now If You Insert Any Value In Your Table Except New Column Then Default Value 1 Will Insert Into New Column

2. If You Want To Drop Column Having Default Value, Then You Will Have To Drop Default Constraint

ALTER TABLE Table_Name DROP CONSTRAINT default_deleted

3. After Deleting Default Constraint, You Can Drop Column

ALTER TABLE Table_Name DROP COLUMN Column_Name