title: Is there a way to create a constraint in a table column to prevent duplicate entries?
body: <p>I am trying to have access constrain duplicate entries in a column.</p>
  
  <p>The reason why is because I have multiple years of salary that can be entered any number of times.</p>
  
  <p>For example,</p>
  
  <pre><code>ID Salary Year
  22 $20000 2013
  22 $15000 2012
  22 $20000 2013 &lt;- Causes duplicate entries in my report
  23 $20000 2013 &lt;- Need to have 2013 here though
  </code></pre>
  
  <p>I want it so that a user cannot enter 2013 more than once in the column of my COMP table.</p>
  
  <p><strong>EDIT:</strong> Added ID numbers because I have multiple people in my COMP table. This changes the question.</p>