title: Left outer Join query returns duplicates in SQL Server
body: <p>I have a table 1 (<code>MID, SSN, ...</code>) <code>MID</code> is primary key and table 2 (<code>ID, SSN, StateCode..</code>) where <code>ID</code> and <code>SSN</code> make up the primary key. I'm trying to display all columns from  table 1 along with <code>StateCode</code> from table 2 matching it against <code>SSN</code>. Tbl 1 has 50 rows and some have same <code>SSN</code> values.</p>
  
  <p>If no <code>SSN</code> match is found from table 2, displaying a NULL in <code>StateCode</code> is acceptable, so I chose left join. Here is my query</p>
  
  <pre><code>Select 
      tbl1.*, tbl2.StateCode
  from 
      tbl1
  left outer join 
      tbl2 on tbl1.SSN = tbl2.SSN
  </code></pre>
  
  <p>I'm looking to retrieve 50 records, but I get 70, rows that contain the same ssn value in tbl1 ends up duplicated in the final output. What is going wrong?</p>