SQL | NOT NULL Constraint
This constraint tells that we cannot store a null value in a column. That is, if a column is specified as NOT NULL then we will not be able to store null in this particular column any more.
By default, if you don’t specify the NOT NULL constraint, SQL Server will allow the column to accepts NULL.
Add Not Null constraintIn New Table
Add NOT NULL constraint to an existing column
First, update the table so there is no NULL in the column:
alter the table to change the property of the column:
Removing NOT NULL constraint