title: Inner join returning duplicate records access sql
body: <p>I have the below table. the only difference in data is <strong>suff, wt</strong>; the rest of them look the same.</p>
  
  <p>Things table</p>
  
  <pre><code>  Prefix  Baseletter  suff   CSCcode   Description  WT      BNO      BNO-CSCcode 
  
    EIGC    A5560        BGA    04020    blah1        0       5560      5560-04020
    EIGC    A5560        HEA    04020    blah2        17.9    5560      5560-04020
  </code></pre>
  
  <p>Mapp table</p>
  
  <pre><code>  BNO      BNO-CSCcode    EID    Description   
  
    5560      5560-04020   4005    blah1
    5560      5560-04020   4011    blah2
  </code></pre>
  
  <p>I'm trying to inner join them using <strong>BNO-CSCcode</strong> to get EID for corresponding <strong>BNO</strong>. But my query is returning duplicates. I'm getting 4 records, even though the first table only has two records.</p>
  
  <p>My SQL query:</p>
  
  <pre><code>SELECT 
    Things.Prefix ,
    Things.Baseletter,
    Things.suff,
    Things.CSCcode,
    Things.WT,
    Mapping.BNO-CSCcode,
    Mapping.EID 
  FROM 
    Things 
    INNER JOIN Mapping ON Things.BNO-CSCcode = Mapping.BNO-CSCcode 
  </code></pre>
  
  <p>Why am I getting these duplicates, and how can I fix that?</p>