title: How to get related value between two dataframes
body: <p>If I have two dataframes. Dataframe A have an a_id column, dataframe B have an b_id column and a b_value column. How can I join A and B on a_id = b_id and get C with id and max(b_value)?
  <a href="https://i.stack.imgur.com/hQKEr.png" rel="nofollow noreferrer">enter image description here</a></p>