title: How to get duplicate values from SAS?
body: <p>For a data that has the following variable: Student_ID, Start_week, Sy, Item, Type, School, Tuition and Country. If an observation has a same combination of the (Student_Id, Start_week, Sy, Item, Type and School), it is a duplicate observation. </p>
  
  <p>For instance:</p>
  
  <pre><code>Student_ID Start_week Sy Item Type School
  10001           1     11  101   0    2
  10001           1     11  101   0    2
  </code></pre>
  
  <p>The two observation is a duplicate because it has same value for the combination. What I was doing was by:</p>
  
  <pre><code>proc freq data = mydataset;
   by Student_ID;
   tables Start_week Sy Item Type School;
  run;
  </code></pre>
  
  <p>However, this didn't really help me to see what are duplicates and what are not. I wanted to create a count variable so to count duplicates, but it didn't capture the combination but just the Student_ID. Moreover, by using proc freq, it was running out of memory. </p>
  
  <p>What are some effective ways to identify the duplicate values?</p>