MySQL 8.0

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select version();

version()

8.0.27

create table users(id int , parent_id int);
create table mlm(id int, dat int);

insert into users(id, parent_id) values (2,1), (3,1),(4,1),
(5,1),(6,2), (7,2), (8,4);
insert into mlm(id, dat) values (4, 100), (5,200);
select * from users; select * from mlm;

id
parent_id

2
1

3
1

4
1

5
1

6
2

7
2

8
4

id
dat

4
100

5
200

SELECT DISTINCT u.id, IF(uc.id,1,0) if_cld, IF(m.id,1,0) in_mlm, m.dat
FROM users u
LEFT JOIN users uc ON uc.parent_id = u.id
LEFT JOIN mlm m ON m.id = u.id
WHERE u.parent_id = 1 AND (uc.id OR m.id)

id
if_cld
in_mlm
dat

2
1
0
null

4
1
1
100

5
0
1
200