Why does this query DELETE FROM test WHERE id=(SELECT id FROM (SELECT * FROM test) temp ORDER BY RAND() LIMIT 1); sometimes delete 1 row, sometimes 2 rows and sometimes nothing?

If I write it in this form: SET @var = (SELECT id FROM (SELECT * FROM test) temp ORDER BY RAND() LIMIT 1); DELETE FROM test WHERE id=@var;, then it work correctly - is problem in subquery?

Why does this query

DELETE FROM test 
WHERE id = ( SELECT id 
             FROM (SELECT * FROM test) temp 
             ORDER BY RAND() 
             LIMIT 1
           );

sometimes delete 1 row, sometimes 2 rows and sometimes nothing?

If I write it in this form:

SET @var = ( SELECT id 
             FROM (SELECT * FROM test) temp 
             ORDER BY RAND() 
             LIMIT 1
           ); 
DELETE FROM test 
WHERE id=@var;

then it work correctly - is problem in subquery?

Why this query DELETE FROM test WHERE id=(SELECT id FROM (SELECT * FROM test) temp ORDER BY RAND() LIMIT 1); sometimes delete 1 row, sometimes 2 rows and sometimes nothing?

If I write it in this form: SET @var = (SELECT id FROM (SELECT * FROM test) temp ORDER BY RAND() LIMIT 1); DELETE FROM test WHERE id=@var;, then it work correctly - is problem in subquery?

Why does this query DELETE FROM test WHERE id=(SELECT id FROM (SELECT * FROM test) temp ORDER BY RAND() LIMIT 1); sometimes delete 1 row, sometimes 2 rows and sometimes nothing?

If I write it in this form: SET @var = (SELECT id FROM (SELECT * FROM test) temp ORDER BY RAND() LIMIT 1); DELETE FROM test WHERE id=@var;, then it work correctly - is problem in subquery?