SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function dateDiff (children 1)
     ExpressionList (children 3)
      Literal \'months\'
      Function toDateTime (children 1)
       ExpressionList (children 1)
        Literal \'2017-12-31\'
      Function toDateTime (children 1)
       ExpressionList (children 1)
        Literal \'2016-01-01\'