Mysql 了解查询中ORDER BY的行为

我的目标是 Select 没有老板或他们的老板住在含有字母‘o’或字母‘u’的街道上的员工的全名.然后，我想按全名降序列出它们. 问题出在排序上，因为通过我认为相同的查询，我得到了不同的答案.

当我在MySQL工作台中引入以下命令时:

select concat(surnames,', ',name) as 'Full Name', street
from employee
where boss is null or (boss is not null and (street like'%u%' or steet like '%o%'))
order by concat(surnames,', ',name) desc;

通过这个命令，我得到了我想要的答案，即:

Full Name              Street
Suárez García, Juan Juan Valdés 25
Sarasola Goñi, Vanesa   Austria
Requena Santos, Pilar   Alicante 3
Puertas Elorza, Marta   Lope de Vega 3
Piedra Trujillo, Ramón  Madre Vedruna 21
Narváez Alonso, Alba    Vara de Rey 22
Gómez de la Sierra, Francisco   Loscertales 9
Chávarri Díez, Lorea    
Arrieta Alcorta, Kepa   Urbieta 33
Álvarez González, Ana   Graus 19

但当我更改另一个在我看来相同的顺序时:

select concat(surnames,', ',name) as 'Full Name', street
from employee
where boss is null or (boss is not null and (street like'%u%' or steet like '%o%'))
order by 'FullName' desc;

我得到了一个错误的答案，如下所示:

Full Name               Street
Suárez García, Juan Juan Valdés 25
Puertas Elorza, Marta   Lope de Vega 3
Chávarri Díez, Lorea    
Narváez Alonso, Alba    Vara de Rey 22
Gómez de la Sierra, Francisco   Loscertales 9
Piedra Trujillo, Ramón  Madre Vedruna 21
Sarasola Goñi, Vanesa   Austria
Requena Santos, Pilar   Alicante 3
Álvarez González, Ana   Graus 19
Arrieta Alcorta, Kepa   Urbieta 33

有人能告诉我这是怎么回事吗？