SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Subquery (children 1)
     SelectWithUnionQuery (children 1)
      ExpressionList (children 1)
       SelectQuery (children 2)
        ExpressionList (children 1)
         Literal NULL
        Function isNotNull (children 1)
         ExpressionList (children 1)
          Literal NULL
