Question

Any reason why this will return rows:

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'

Yet this throws a syntax error?

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

It has nothing to do with CONCAT. The problem is that you should not have a FROM clause in an UPDATE statement.

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'