How do I update the records from the SELECT query in MySQL

Question

I am new to MySQL. I have users table. the user has a username and nickname. The username can be null. How do I write a single MySQL query that updates the user's username by a nickname when the user has no username?

Thank you so much for your help!

question from:https://stackoverflow.com/questions/65948804/how-do-i-update-the-records-from-the-select-query-in-mysql

Answer 1

UPDATE tablename
SET username = nickname
WHERE username IS NULL

WHERE prevents updating for a row which has username value set to something, so only rows without the value in this column are updated.