MySQL 8.0

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create table test (
  id integer,
  expire varchar(5),
  lastwdif varchar(255),
  name varchar(255),
  vendor varchar(255)
);
insert into test values
  (10, '10/01', 'd23dv36', 'Juan', '25,5'),
  (15, '12/04', '2232cg', 'Maria', '35,4'),
  (15, null, null, 'Maria', '14,1'),
  (10, '12/17', '2232cg', 'Juan', '10,2'),
  (10, null, null, 'Juan', '32,10');

Records: 5  Duplicates: 0  Warnings: 0


select t1.id, t1.expire, t2.lastwdif, t2.name, t2.vendor
from test t1
join test t2 on t1.id = t2.id and t2.expire is null
where left(t1.expire, 3) = '12/'
order by id;


id
expire
lastwdif
name
vendor


10
12/17
null
Juan
32,10

15
12/04
null
Maria
14,1