SQL: Max ID Group By With Condition - mysql

Question

I'm a SQL newbie, here is my Table:
+----+--------+---------+------------+
| ID | Person | Success | Message |
+----+--------+---------+------------+
| 1 | Alice | 1 | Hello |
+----+--------+---------+------------+
| 2 | Bob | 0 | World |
+----+--------+---------+------------+
| 3 | Alice | 0 | Foo |
+----+--------+---------+------------+
| 4 | Clark | 1 | Bar |
+----+--------+---------+------------+
And I want to select latest (MAX ID assuming ID is incremental) records which is success for each person
Expected result:
+----+--------+---------+------------+
| ID | Person | Success | Message |
+----+--------+---------+------------+
| 4 | Clark | 1 | Bar |
+----+--------+---------+------------+
// Alice's latest record is not success, ignore
// Bob has no success record, ignore
Here is my current approach:
SELECT *
FROM test AS t1
RIGHT JOIN (
SELECT MAX(id) AS max_id
FROM test
GROUP BY Person
) AS t2
ON t1.id = t2.max_id
WHERE t1.success = 1
// Select Max ID group by person, join with original table, then filter by success
And I'm wondering if there are better approach or neater SQL lines for this?
Thank you so much!

Answer 1

SELECT *
FROM test t1
WHERE Success
AND NOT EXISTS ( SELECT NULL
FROM test t2
WHERE t2.id > t1.id
AND t1.person = t2.person
AND NOT Success );
SELECT t1.*
FROM test t1
LEFT JOIN t2 ON t1.person = t2.person
AND t2.id > t1.id
AND NOT t2.Success
WHERE t1.Success
AND t2.id IS NULL;

Answer 2

Use ROW_NUMBER to filter down to the latest record for each person. Then, subquery and retain only success records:
WITH cte AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY Person ORDER BY ID DESC) rn
FROM test
)
SELECT ID, Person, Success, Message
FROM cte
WHERE Success = 1;
For an old school way of doing this, if perhaps you are still using MySQL 5.7, we can try:
SELECT t1.ID, t1.Person, t1.Success, t1.Message
FROM test t1
INNER JOIN
(
SELECT Person, MAX(ID) AS MAX_ID
FROM test
GROUP BY Person
) t2
ON t2.Person = t1.Person AND
t2.MAX_ID = t1.ID
WHERE
t1.Success = 1;

Answer 3

You could use:
select * from test t1
where exists (
select 1 from test
where success
having max(id) = t1.id
)
Sql fiddle
Alternative query:
select * from test t1
where id = (
select max(id) from test
where success
)
Sql fiddle

Answer 4

And I want to select latest (MAX ID assuming ID is incremental) records which is success for each person
One way to do this uses a correlated subquery like this:
select t.*
from test t
where t.status = 'success' and
t.id = (select max(t2.id) from test t2 where t2.person = t.person);
This is pretty much a direct translation of what you are asking. The condition on id is the "latest record" for each person. The status = 'success' is the filter you want.