title: How to join two tables by one or another ID column (python pandas)?
body: <p>I am using Python pandas, I would appreciate the code in Python. But you can suggest a solution in Excel or SQL. I have two tables A and B. Table A has two ID columns by which I want to join table B. Table B has one ID column that either corresponds with one or the other ID column of Table A. Here is an example:</p>
  <p><a href="https://i.stack.imgur.com/jdKAX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jdKAX.png" alt="enter image description here" /></a></p>
  <p><a href="https://i.stack.imgur.com/ENIZu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ENIZu.png" alt="enter image description here" /></a></p>
  <p>And this is the resulting table AB that I want:
  <a href="https://i.stack.imgur.com/Bfp8F.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Bfp8F.png" alt="enter image description here" /></a></p>