MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table t1(id int, apn int, title varchar(100),genre varchar(100),trailer varchar(100))
insert into t1 values (1,1234567,'TinTin',null,null), 
(2,1234567,'TinTin','Fiction','youtube.xyz'),
(3,1234567,'TinTin','Fiction',null)

Records: 3  Duplicates: 0  Warnings: 0


DELETE m1 FROM t1 m1
where id not in ( select * from 
                                 ( select max(id) from t1 where trailer is not null group by apn
                                ) A
                               
                )
select * from t1


id
apn
title
genre
trailer


2
1234567
TinTin
Fiction
youtube.xyz