I'm trying to filter, so the column salaryMonth only contains data which has 2020 inside, so 2019 is filtering out. 
SELECT sum(km_amount) as total
     , user_id
     , salaryMonth 
  from kms
     , users 
 where users.id = kms.user_id 
 group 
    by salaryMonth
     , user_id 

 
     
     
    