In code such as the following, what is the need to write `constraint pk_dept primary key (deptno)` if just simply `primary key (deptno)` works? Is `pk_dept` something the database uses internally, since it doesn't seem to be a visible part of the table?

```
create table dept
    (deptno decimal(2,0),
    dname  varchar(14),
    loc varchar(13),
    constraint pk_dept primary key (deptno));

```