MySQL 8.0

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create table test (userID int,  fName varchar(20), lName varchar(20), reportsTo int)
insert into test values(1, 'anna', 'foo',   null)
insert into test values(2, 'john', 'bar',   1)
insert into test values(3, 'mary', 'quux',   2)
insert into test values(4, 'paul', 'faa',   2)
insert into test values(5, 'dan', 'ber',   4)
select * from test
where userID in (select reportsTo from test);


userID
fName
lName
reportsTo


1
anna
foo
null

2
john
bar
1

4
paul
faa
2