title: Adding hours to a timestamp column in Sqlite results in NULL, Why?
body: <p>I am getting NULL (nothing) from: </p>
  
  <p><strong>SELECT DATETIME(ServiceCall_CreatedOn,'-6 hours')  AS 'Service Created On:'</strong> ...</p>
  
  <p>Where ServiceCall_CreatedOn is a Sqlite text column containing:
  "2019-01-20 4:48:11" (without the quotes of course)</p>
  
  <p>The following:</p>
  
  <p><strong>SELECT ServiceCall_CreatedOn  AS 'Service Created On:'</strong> ...</p>
  
  <p>and the following</p>
  
  <p><strong>SELECT DATETIME('2019-01-20 4:48:11','-6 hours')  AS 'Service Created On:'</strong> ...</p>
  
  <p>do work!!!!! </p>
  
  <p>Why SQLite DATETIME time subtraction work with a date literal and not with the ServiceCall_CreatedOn column on it? What may be a solution?</p>
  
  <p><a href="https://i.stack.imgur.com/ZGkgV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZGkgV.png" alt="Problem in one picture"></a></p>