Question

I need to write a query to retrieve values from two columns using mysql table

My table has the following strucutre

| ID | to_user_id | from_user_id |  message  |        datetime     | 
| 1  |     21     |      07      |    hi     | 2012-05-10 04:13:01 | 
| 2  |     07     |      21      |   hello   | 2012-05-10 04:17:51 | 
| 3  |     21     |      11      | what's up | 2012-05-10 04:21:51 |
| 4  |     21     |      02      |  hi dude  | 2012-05-10 04:43:51 |

I want to write a query to get only latest message from all from_user_id’s

i will try with

$query="select * from messages WHERE datetime = (SELECT MAX(datetime) FROM messages)";

but it has error shown

Unknown column ‘datetime’ in ‘where clause’

Answer 1

You can also try:

select a.from_user_id, a.message
from table1 a
WHERE a.datetime = (SELECT MAX(datetime) FROM table1 x WHERE x.from_user_id = a.from_user_id)