@Rohan, You can send a mail to firstname.lastname@example.org with your queries if you face any issues in teradata.
in simple ppi is used to store and retrive the data in partition wise
exampel i want to retirve data of a particular department . in where clause i will mention partition column deptno . so that data will be retrived very fastly because particular dept. data will be stored in one partition in amps.
select *from emp where deptno=20;
secondary index are an alternative path for accessing the data. comparetively full table scan it is faster. it is used in some cases like other than primary index in our where clause frequently using. like by last_name column wise or by area wise
select *from emp where emp_loc='new york';