title: SQL - select all rows from table where a column contains only digits
body: <p>I want to find all rows in which a column contains only digits.</p>
  
  <p>The first idea was using <code>LIKE [0-9]%</code>, but in fact this matches any strings starting with a digit.</p>
  
  <p>It seems to be a very simple task, but unfortunately I can't find solution</p>