Oracle PL/SQL/Constraints/Name for Primary Key

Primary keys can explicitely be named

SQL> -- Primary keys can explicitely be named.
SQL> -- create table statement creates a table with a primary key whose name is pk_name.
SQL>
SQL> create table myTable (
  2    a number,
  3    b number,
  4    c number,
  5    constraint pk_name primary key (a, b)
  6  );
Table created.
SQL>
SQL>
SQL> insert into myTable values (1,2,3);
1 row created.
SQL> insert into myTable values (1,4,3);
1 row created.
SQL> insert into myTable values (1,3,3);
1 row created.
SQL> insert into myTable values (1,5,3);
1 row created.
SQL> insert into myTable values (1,2,3);
insert into myTable values (1,2,3)
*
ERROR at line 1:
ORA-00001: unique constraint (SYS.PK_NAME) violated

SQL>
SQL> select * from myTable;
         A          B          C
---------- ---------- ----------
         1          2          3
         1          4          3
         1          3          3
         1          5          3
SQL>
SQL> drop table myTable;
Table dropped.
SQL>
SQL>