create table t1 (c1 int, c2 int, c3 int);

insert into t1 values (1,2,3),(4,5,6);

create table t2 like t1;

insert into t2 values (7,8,9),(10,11,12);

create view v1 as

select * from (

    select *, a1 from (

        select c1, c2, c3 from t1 where c1 > 1

        ) as d1 (a1, a2, a3)

    union 

    select *, 1 as c4 from t2 order by a2

) d2 (o1, o2, o3, o4);

prepare stmt from "select * from v1";

execute stmt;

drop view v1;

drop tables t1, t2;

query 'execute stmt' failed: ER_BAD_FIELD_ERROR (1054): Unknown column 'a2' in 'ORDER BY'