SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function tupleElement (children 1)
     ExpressionList (children 2)
      Identifier t1
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'a\'
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier t_tuple_element