How to use NOT NULL in sql server

NOT NULL

This  constraint is used to void the acceptance of null value in the column of the table. by default a column has NULL constraints means that columns can hold the null value.

Example

Following is the example to apply NOT NULL Constraint on CREATE TABLE

CREATE TABLE Employee

(

Id int NOT NULL CHECK (Id>0),

Name varchar(255) NOT NULL,

Address varchar(255),

Age int,
)


you can also apply NOT NULL constraint on existing table as below query

ALTER TABLE Employee

MODIFY age  INT NOT NULL;