After merge fixes

insert into t1 values (0);

insert into t2 values (1);

create table t3 engine=merge union=(t1, t2) select * from t1;

INSERT TABLE 't1' isn't allowed in FROM table list

ERROR HY000: You can't specify target table 't1' for update in FROM clause

create table t3 engine=merge union=(t1, t2) select * from t2;

INSERT TABLE 't2' isn't allowed in FROM table list

ERROR HY000: You can't specify target table 't2' for update in FROM clause

drop table t1, t2;

ERROR HY000: You can't specify target table 't1' for update in FROM clause

select a from t1 union select a from t2 order by t2.a;

ERROR 42S02: Unknown table 't2' in order clause

drop table t1;

drop table t1,t2;

select length(version()) > 1 as `*` UNION select 2;

*

create table t1 (a int);

insert into t1 values (0), (3), (1), (2);

explain (select * from t1) union (select * from t1) order by a;

table	type	possible_keys	key	key_len	ref	rows	Extra

t1	ALL	NULL	NULL	NULL	NULL	4	

t1	ALL	NULL	NULL	NULL	NULL	4	

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	

2	UNION	t1	ALL	NULL	NULL	NULL	NULL	4	

NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	Using filesort

drop table t1;

CREATE TABLE t1 (  id int(3) unsigned default '0') ENGINE=MyISAM;

INSERT INTO t1 (id) VALUES("1");

create table t1 select a from t1 union select a from t2;

--error 1109

select a from t1 union select a from t2 order by t2.a;

drop table t1;   # Drop temporary table

drop table t1,t2;

#