Copy Table With or Without Data Using Create Table As statement

1. How to copy both the structure and data of a table

      create table emp_copy

      as

      select * from emp;

2. How to copy specific columns of a table along with their data.

     create table emp_copy

     as

     select empno, sal from emp;

3. How to copy only the structure of the table without the data.

    create table emp_copy

    as

    select * from emp

     where 1=0;