あなたは例えば次のクエリを使用できます。実際には
select * from teams t1 where `timestamp`=(select min(t2.`timestamp`) from teams t2 where t2.team = t1.team);
を:
[localhost:21000] > create table teams(id int, animal string, `timestamp` timestamp, team string);
[localhost:21000] > insert into teams values (1, "dog", "2016-08-01", "blue"), (2, "cat", "2016-08-02", "blue"), (3, "bird", "2016-07-05", "red"), (4, "cow", "2016-08-04", "red"), (5, "snake", "2016-08-12", "yellow");
[localhost:21000] > select * from teams t1 where `timestamp`=(select min(t2.`timestamp`) from teams t2 where t2.team = t1.team);
+----+--------+---------------------+--------+
| id | animal | timestamp | team |
+----+--------+---------------------+--------+
| 1 | dog | 2016-08-01 00:00:00 | blue |
| 3 | bird | 2016-07-05 00:00:00 | red |
| 5 | snake | 2016-08-12 00:00:00 | yellow |
+----+--------+---------------------+--------+