MySQL: Group by and Order by Max Date

Question

+--------------+-----------------+-----------+---------------------+
| hierarchy_id | title           | parent_of | created_date        |
+--------------+-----------------+-----------+---------------------+
|            1 | Muscat          |         0 | 2014-01-01 00:00:00 |
|            2 | Bahrain         |         1 | 2014-01-01 00:00:00 |
|            3 | Kuwait          |         2 | 2014-01-01 00:00:00 |
|            4 | Jordan          |         2 | 2014-01-25 00:00:00 |
+--------------+-----------------+-----------+---------------------+

hierarchy_id 3 and 4 has same "parent_of" 2. I want to select only one from them which has max date.

My Expected Result is:

+--------------+-----------------+-----------+---------------------+
| hierarchy_id | title           | parent_of | created_date        |
+--------------+-----------------+-----------+---------------------+
|            1 | Muscat          |         0 | 2014-01-01 00:00:00 |
|            2 | Bahrain         |         1 | 2014-01-01 00:00:00 |
|            4 | Jordan          |         2 | 2014-01-25 00:00:00 |
+--------------+-----------------+-----------+---------------------+

Answer 1

you can select max of created_date and then group by parent_of. A query will look like this

SELECT max(hierarchy_id) as hierarchy_id,title,parent_of,max(created_date) as created_date  
FROM tableName
GROUP BY parent_of

Answer 2

If we assume that the ids are assigned in ascending order, then you can just use max() on the first and last columns:

select max(hierarchy_id) as hierarchy_id, title, parent_of, max(created_date) as created_date  
from table t
group by title, parent_of;