MySQL 8.0

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select @@version;

@@version

8.0.36

create table newtable (config_id int, name varchar(20));
create table oldtable (oldtable_id int, name varchar(20), value int);
create table associativetable (config_id int, oldtable_id int);
insert into newtable values (12,null),(22,null);
insert into oldtable values (1,'Jack',10),(2,'Frank',22);
insert into associativetable values (12,1),(22,2);
select * from newtable;
select * from oldtable;
select * from associativetable;

Records: 2  Duplicates: 0  Warnings: 0

Records: 2  Duplicates: 0  Warnings: 0

Records: 2  Duplicates: 0  Warnings: 0

config_id
name

12
null

22
null

oldtable_id
name
value

1
Jack
10

2
Frank
22

config_id
oldtable_id

12
1

22
2

update newtable n
  set n.name = (SELECT name FROM oldtable o JOIN associativetable a ON o.oldtable_id = a.oldtable_id AND a.config_id = n.config_id  )  

Rows matched: 2  Changed: 2  Warnings: 0

select * from newtable;

config_id
name

12
Jack

22
Frank

config_id	name
12	null
22	null