mysql按SUM（column）组排序，另一列

我有以下数据库表：

create table table1 (
col1 VARCHAR(5) NOT NULL,
col2 VARCHAR(5) NOT NULL,
col3 TINYINT NOT NULL,
col4 INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY);

INSERT INTO table1 VALUES
('b','c',1,NULL),
('b','d',2,NULL),
('a','e',1,NULL),
('a','f',3,NULL); 

mysql> select * from table1;
+------+------+------+------+
| col1 | col2 | col3 | col4 |
+------+------+------+------+
| b    | c    |    1 |    1 |
| b    | d    |    2 |    2 |
| a    | e    |    1 |    3 |
| a    | f    |    3 |    4 |
+------+------+------+------+
4 rows in set (0.00 sec)

我想创建一个查询，该查询按col1上的SUM（col3）GROUP排序行。然后，我需要订购col3 DESC。

So final table will look like:
+------+------+------+------+
| col1 | col2 | col3 | col4 |
+------+------+------+------+
| a    | f    |    3 |    4 |
| a    | e    |    1 |    3 |
| b    | d    |    2 |    2 |
| b    | c    |    1 |    1 |
+------+------+------+------+

i can get the SUM(col1):
mysql> select sum(col3) from table1 group by col1;
+-----------+
| sum(col3) |
+-----------+
|         4 |
|         3 |
+-----------+

但不确定如何进行。任何帮助表示赞赏。