add column with default null in sql code example

Example 1: add column table sql default value

ALTER TABLE users
ADD visit_number INT DEFAULT 0;

Example 2: 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.