drop table if exists tt1;
create table tt1(c1 int primary key, c2 int);
insert into tt1 values(1,4);
insert into tt1 values(2,3);
select c1, c2 as c1 from tt1;
c1	c1
1	4
2	3
select c1, c2 as c1 from tt1 order by c1;
ERROR 23000: Column 'c1' in order clause is ambiguous
select c2 as c1 from tt1 order by c1;
c1
3
4
select c2 as c1 from tt1 where c1<4;
c1
4
3
select c1 as cc, c2 as c1 from tt1 where c1<4;
cc	c1
1	4
2	3
select c1 as cc, c2 as c1 from tt1 order by c1;
cc	c1
2	3
1	4
select c1, c2 as c1 from tt1 where c1<4;
c1	c1
1	4
2	3
select c2 as cc from tt1  order by c1;
cc
4
3
select c2 as c1 from tt1 order by c1;
c1
3
4
select c1 as c1, c2 as c1 from tt1 where c1<4;
c1	c1
1	4
2	3
show columns from tt1;
Field	Type	Null	Key	Default	Extra
c1	int(11)	NO	PRI	NULL
c2	int(11)	YES		NULL