How to delete duplicate records in a table ?

For deleting duplicate records we have different ways.I have a Product_table.

Table name: product_table

product_id product_name

       1             xyz

       1             xyz

      30            abc

      30            abc

       5             ttt

Using rowid remove the duplicate records.This query will work only SQL

Syntax: delete from <table name> where rowid not in( select max(rowid) from <table_name> group by <col>);

Query: delete from product_table where rowid not in(select max(rowid) from

product_table group by product_id);

This is another way to delete duplicates. This will work in teradata.

here first create a set table with the definition  then insert the records into set table. Al ready we know the set table does not allow duplicate records. 

create set table product_table_t as (select * from product_table) with no data;

insert into product_table_t select * from product_table;

drop table product_table;

rename table product_table_t as product_table

using distinct, eliminating duplicate records

create temporary table with no data

Query : create table product_t as (select * from product_table) with no data

insert records in to table product_t with using distinct

insert into product_t select distinct * from product_table

drop the the product_table

rename table

rename table product_t as product

Please comment here if you know any other method of removing duplicates.