mysql syntax update record based on other record same table

Question

How do i make sql syntax on mysql, when i want to update parent_id based on id on the other record on the same table with the same value on specific column field, example field Code

i tried to make the following

update product_class t1
set t1.parent_id = t2.id
WHERE t1.family_code <>'' and t1.class_code = ''
join product_class t2
on 
(t1.segment_code = t2.segment_code)

but gives me error

Here is the table structure:

Answer 1

Here is the correct syntax:

update product_class t1 join
       product_class t2
       on t1.segment_code = t2.segment_code
    set t1.parent_id = t2.id
    where t1.family_code <> '' and t1.class_code = '';

The join is part of the update clause in MySQL.

NOTE: the query doesn't look like it would do the right thing. You are doing a self-join on what looks like a non-unique column, which will generate lots of matches. An arbitrary matching row would then be used for the update .