Name already been used by an existing constraint after renaming the table and creating a new one I would like to know why, if I alter a table name to different name and then create a table with the same name, I am getting the error "name already been used by existing constraint". 

This is the create table code

   create table abc
  (
       num number (4),
       name varchar2 (50),
      constraint abc primary key (num, name)
 );


This is the alter table code

 alter table abc rename to cba;


This is  the code to recreate the table 

   create table abc
  (
       num number (4),
       name varchar2 (50),
      constraint abc primary key (num, name)
 );
After renaming the table, rename the constraint and the index as well:

alter table cba rename constraint abc to cba;
alter index abc rename to cba;