Something

mysql> describe test1;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | YES  |     | NULL    |       |
| data  | varchar(40) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
 
 
mysql> select * from test1;
+------+-------+
| id   | data  |
+------+-------+
|    1 | yes   |
|    1 | no    |
|    2 | myabe |
+------+-------+

 
mysql> select * from test1 group by (id);
+------+-------+
| id   | data  |
+------+-------+
|    1 | yes   |
|    2 | myabe |
+------+-------+

We lost the no info