奇CONCAT錯誤與選擇/插入

Question

有什麼理由，這將返回行：

select users.user_fullname,concat(persons.first_name,' ',persons.last_name) 
from users, persons 
where users.user_id = persons.user_id 
and users.user_fullname = '0' 

然而，這將引發一個語法錯誤？

update users 
set users.user_fullname = concat(persons.first_name,' ',persons.last_name) 
from users, persons 
where users.user_id = persons.user_id 
and users.user_fullname = '0' 

Answer 1

它與CONCAT無關。問題是您在UPDATE語句中不應該有FROM子句。

UPDATE users, persons 
SET users.user_fullname = CONCAT(persons.first_name,' ',persons.last_name) 
WHERE users.user_id = persons.user_id 
AND users.user_fullname = '0'