title: Primary key on table
body: <p>I have table table with featureid,ParameterID,MeasurementDateTime,ParameterValue  will never be duplicated so we have composite key of featureid,ParameterID,MeasurementDateTime. Data is like this</p>
  
  <pre><code> FeatureID  ParameterID MeasurementDateTime ParameterValue
     ASt-1    AP1         1/1/2009 0:00   0.00866667
     ASt-1    AP1         1/1/2009 1:00   0.00608333
     ASt-1    AP1         1/1/2009 2:00   0.016
     ASt-1    AP2         1/1/2009 3:00   0.01091667
     ASt-1    AP2         1/1/2009 4:00   0.01333333
     ASt-1    AP2         1/1/2009 5:00   0.01091667
     ASt-1    AP2         1/1/2009 6:00   0.0195
     ASt-2    AP1         1/1/2009 7:00   0.00733333
     ASt-2    AP1         1/1/2009 8:00   0.02075
     ASt-2    AP1         1/1/2009 9:00   0.00966666
     ASt-2    AP2         1/1/2009 10:00  0.01208333
     ASt-2    AP2         1/1/2009 11:00  0.00966667
     ASt-2    AP2         1/1/2009 12:00  0.01466667
     ASt-2    AP3         1/1/2009 13:00  0.02041666
     ASt-3    AP1         1/1/2009 14:00  0.01233333
     ASt-3    AP1         1/1/2009 15:00  0.0265
     ASt-3    AP1         1/1/2009 16:00  0.011
     ASt-3    AP1         1/1/2009 17:00  0.01383333
     ASt-3    AP2         1/1/2009 18:00  0.0135
     ASt-3    AP3         1/1/2009 19:00  0.009
  </code></pre>
  
  <p>The where clause in most of the queries will be.</p>
  
  <pre><code> 1. featureid,ParameterID,year(MeasurementDateTime) 
   2. featureid,ParameterID,year(MeasurementDateTime) and month(MeasurementDateTime)
   3. featureid,ParameterID
  </code></pre>
  
  <p>Please note data is inserted after every one hour and there are nearly 5000 inserts.</p>
  
  <p>Question 1: Is this ok for our data or we should create another non-clustered index on featureid,ParameterID?</p>
  
  <p>Question 2 : Do we need re-index our data periodically?</p>