Table A
trx_id | charge | user_id
  1    |   20   |  007
  2    |   10   |  008
  3    |   10   |  007

Table B
user_id | name
  007   | Alex
  008   | Adam

user_id | user_name | totalCharge
  007   |   Alex    |     30
  008   |   Adam    |     10