title: merge or left join R
body: <p>I have three datasets that has same Index column (Key), StudentId, and all have same number of observations, I repeat same number of observations, but different columns and different values for each observation.</p>
  
  <pre><code>    Dataset 1
      Id     Lab 
       1      33     
       .      .
       2334   98
  
      Dataset 2
      Id     Sports
       1      83     
       .      .
       2334   933
  
      Dataset 3
      Id     Lunch
       1      33     
       .      .
       2334   238
  </code></pre>
  
  <p>I dont know why when I use merge or left_merge to combine all the three datasets the final dataset shows up more number of rows than it should man ?</p>
  
  <pre><code>    Dataset Final
      Id     Sports   Lunch     Lab
       1      33       83       33 
       .      .
       3564   98       34       56
  </code></pre>