Answer by Erfan Mohammadi for How to add a column with a default value to an existing table in SQL Server?

--Adding New Column with Default ValueALTER TABLE TABLENAME ADD COLUMNNAME DATATYPE NULL|NOT NULL DEFAULT (DEFAULT_VALUE)

OR

--Adding CONSTRAINT And Set Default Value on ColumnALTER TABLE TABLENAME ADD  CONSTRAINT [CONSTRAINT_Name]  DEFAULT (DEFAULT_VALUE) FOR [COLUMNNAME]