Check Constraint:- Check Constraint is used to limit the range of the values, Which can be entered into a column.
The general formula for check constraint in sql server
Alter tabla (tablname) add constraint (constraint name) check (Boolean expression )
If the Boolean expression return true, then the check constraint allow he value, otherwise it dose not. Since Age is a nullable Column, its possible to pass null for tis column, When inserting row. When you pass NULL for the AGE column, the boolean expression evaluates to unknown, and allows the values.
