Question about updating data in MySQL [update] cannot be successful

Question

Answer 1

Change to where id IS NULL That’s it
The equal sign cannot be used to determine NULL in MySQL.

For details, please see:
https://dev.mysql.com/doc/ref...

Answer 2

where id is null

Answer 3

General update statements, to be on the safe side, first verify the data volume and confirm the update content

#update defaultdemo
#set id = 19
select id 
from defaultdemo
where id is null;