SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 3)
   ExpressionList (children 1)
    Function or (children 1)
     ExpressionList (children 2)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier x
        Identifier y
      Function and (children 1)
       ExpressionList (children 2)
        Function isNull (children 1)
         ExpressionList (children 1)
          Identifier x
        Function isNull (children 1)
         ExpressionList (children 1)
          Identifier y
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier t1
   ExpressionList (children 1)
    OrderByElement (children 1)
     Identifier x
