title: merging two files based on two columns
body: <p>I have a question very similar to a previous post:
  <a href="https://stackoverflow.com/questions/9575972/merging-two-files-by-a-single-column-in-unix">Merging two files by a single column in unix</a>
  but i want to merge my data based on two columns (The orders are the same, so no need to sort).
  Example,</p>
  
  <p>subjectid subID2 name age<br>
  12 121 Jane 16<br>
  24 241 Kristen 90<br>
  15 151 Clarke 78<br>
  23 231 Joann 31  </p>
  
  <p>subjectid subID2 prob_disease<br>
  12 121 0.009<br>
  24 241 0.738<br>
  15 151 0.392<br>
  23 231 1.2E-5  </p>
  
  <p>And the output to look like</p>
  
  <p>subjectid SubID2 prob_disease name age<br>
  12 121 0.009 Jane 16<br>
  24 241 0.738 Kristen 90<br>
  15 151 0.392 Clarke 78<br>
  23 231 1.2E-5 Joanna 31   </p>
  
  <p>when i use join it only considers the first column(subjectid) and repeats the SubID2 column.
  Is there a way of doing this with join or some other way please? Thank you </p>