What is the use with primary index ?

when i am creating a primary key in database level automatically it will create a primary index

and it will restrict the duplicate and null values

but here after assigning the index to primary index still it accepts the null values (if the prop what u said set to no)

What i understood from u r reply is:

Here we are using primary index to fetch the data quickly from X++

By default it will not add any more costraint to that field… is this ?