title: Find a number with Oracle regexp that has an exact length of 3
body: <p>I want to get only 456.</p>
  
  <p>I tried this regular expression, but I got all numbers which contain 3 digit characters, 456, 46354376, etc.</p>
  
  <pre><code>select regexp_substr(MY_COLUMN,'([[:digit:]]{3})') from MY_TABLE
  </code></pre>