title: SQL Server's ISNUMERIC function
body: <p>I need to checking a column where numeric or not in SQL Server 2012.</p>
  
  <p>This my case code.</p>
  
  <pre><code>CASE
      WHEN ISNUMERIC(CUST_TELE) = 1 
        THEN CUST_TELE 
        ELSE NULL 
  END AS CUSTOMER_CONTACT_NO
  </code></pre>
  
  <p>But when the <code>'78603D99'</code> value is reached, it returns <code>1</code> which means SQL Server considered this string as numeric.</p>
  
  <p>Why is that?</p>
  
  <p>How to avoid this kind of issues?</p>