Partitioning divides the larger dataset into smaller ones so that efficiency in processing the query increases. But if you do indexing it won’t divide the dataset into smaller ones, rather it would create another table containing all the details of the table which you are indexed. So when you try to execute any query on an indexed table it will first query on the index_table based on the data in the index it will directly query on the original table. It is just like the index of any text book.