title: Check if string consists of letters or numbers only in Transact-SQL
body: <p>How can I check if a string consists of letters or numbers ONLY in Transact-SQL?</p>
  <p>Here the string has datatype <code>nchar</code>, 'letters' specifically refer to latin characters. Database environment is Microsoft SQL Server 2014.</p>
  <p>Example for desired result:</p>
  <pre><code>C172E returns True
  412?A returns False  //'?' is neither a letter nor a number
  </code></pre>
  <p>I've done some searching but only found the built-in <code>ISNUMERIC()</code> function, which is for numbers only.</p>
  <p>Is there a Transact-SQL solution for this problem?</p>