title: AWK replace a column value when occurrences happen
body: <p>.
  Hi everyone!</p>
  
  <p>I need to replace some values in FILE2 file with the values on FILE1 file when date and time match.</p>
  
  <p><strong>FILE1</strong></p>
  
  <pre>
  121216, 0100, 1.1,
  121216, 0115, 1.0,
  121216, 0130, 2.1,
  121216, 0145, 1.8,
  121216, 0200, 1.5,
  121216, 0215, 1.3,
  121216, 0230, 0.9,
  121216, 0245, 1.2,
  </pre>
  
  <p><strong>FILE2</strong></p>
  
  <pre>
  121216, 0100, 2.3,
  121216, 0200, ,
  </pre>
  
  <p><strong>OUTPUT</strong></p>
  
  <pre>
  121216, 0100, 1.1,
  121216, 0200, 1.5,
  </pre>
  
  <p>Please an awk solution, speed is needed.</p>
  
  <p>Thanks in advance!</p>