Access Variable in Javascript function

Question

I try to read some data from a MS-SQL database with jquery ajax:

function lesen() {
  var d;
  var sqlWhere = "SELECT * FROM Benutzer";
  $.ajax({
    type: 'POST',
    url: './en.php',
    data: {
      daten: sqlWhere
    }
  }).done( function (data) {
    d = $.parseJSON(data);
    return d;
  })
}

console.log( lesen() );

console.log( lesen () ) retuns "undefined"

And here is my question: How do I use the values which I return in the "lesen()" function? How can I access the data outside of the function?

Thank you!