title: How can I match the same column value in different tables?
body: <p>I have two tables, Table A is the parent, Table B is the child. Both tables have the column "order_number".</p>
  
  <p>I want to find the value in the "order_number" column in Table A, that matches the value of the "order_number" column in Table B, then I'll save the "id" of the Table A record in another column of the Table B record.</p>
  
  <p>I'm having trouble coming up with an activerecord query to find the matching column value. How should I do that?</p>