You can‘t specify target table ‘backup‘ for update in FROM clause

在执行update语句是遇到：You can’t specify target table ‘backup’ for update in FROM clause

update `backup` set file_size = 1.11 where backup_time = 
select max(backup_time) backup_time  
from `backup` 
where task_id = 1)

不能在from字句中使用要update的表。

此时我们可以用一个起别名的中间表

update `backup` set file_size = 1.25 where backup_time = 
(select b.backup_time 
from 
(select max(backup_time) backup_time  
from `backup` 
where task_id = 1) b )