Difference between year by year customer sales

Version 1

    I have two tables

    Table 1: Contains 2017 customer sales data as below

     

    Date                         Customer Name          Amount

    01-04-2017                aaa                              100    

    09-04-2017                 bbb                              200         

    17-04-2017                  ccc                              500    

    28-04-2018                 ddd                              1000

    28-04-2018                  eee                              2000

    Table 2 : Contains 2018 Customer sales data as blow

     

    Date                     Customer Name          Amount

    04-05-2018             aaa                              500

    11-04-2018             ccc                               700

    22-04-2018             ddd                               900

     

    How to calculate difference between the amount per customer over year

    How to calculate difference between the amount percentage per customer over year