sum - case when

select 
 channel
 ,SUBSTR(paid_date,1,7) AS YYMM
 ,SUM(orders) AS sum_orders
from report_daily_sales_by_channel_by_store
where paid_date >= '2019-10-01'                            
and   paid_date <  '2020-01-01' 
group by channel, SUBSTR(paid_date,1,7)
;
+----------+----------+-------------+
| channel  |   yymm   | sum_orders  |
+----------+----------+-------------+
| SNG      | 2019-10  | 21154085    |
| SNG      | 2019-11  | 20433075    |
| SNG      | 2019-12  | 21052846    |
| WMDJ     | 2019-10  | 1803969     |
| WMDJ     | 2019-11  | 1833128     |
| WMDJ     | 2019-12  | 972400      |
| JDDJ     | 2019-10  | 3229328     |
| JDDJ     | 2019-11  | 3015826     |
| JDDJ     | 2019-12  | 2975539     |
| WFS      | 2019-10  | 414686      |
| WFS      | 2019-11  | 596486      |
| WFS      | 2019-12  | 410759      |
| OFFLINE  | 2019-10  | 25583525    |
| OFFLINE  | 2019-11  | 22955407    |
| OFFLINE  | 2019-12  | 23555036    |
+----------+----------+-------------+

 

select 
 YYMM
 ,sum(case when channel='SNG'     then sum_orders else 0 end)   AS SNG_orders
 ,sum(case when channel='WMDJ'    then sum_orders else 0 end)   AS WMDJ_orders
 ,sum(case when channel='JDDJ'    then sum_orders else 0 end)   AS JDDJ_orders
 ,sum(case when channel='WFS'     then sum_orders else 0 end)   AS WFS_orders
 ,sum(case when channel='OFFLINE' then sum_orders else 0 end)   AS OFFLINE_orders
from ( 
--1
select 
  channel
  ,SUBSTR(paid_date,1,7) AS YYMM
  ,SUM(orders) AS sum_orders
from report_daily_sales_by_channel_by_store
where paid_date >= '2019-10-01'                            
and   paid_date <  '2020-01-01' 
group by channel, SUBSTR(paid_date,1,7)
--end1
) AS a
group by YYMM
order by YYMM ;
+----------+-------------+--------------+--------------+-------------+-----------------+
|   yymm   | sng_orders  | wmdj_orders  | jddj_orders  | wfs_orders  | offline_orders  |
+----------+-------------+--------------+--------------+-------------+-----------------+
| 2019-10  | 21154085    | 1803969      | 3229328      | 414686      | 25583525        |
| 2019-11  | 20433075    | 1833128      | 3015826      | 596486      | 22955407        |
| 2019-12  | 21052846    | 972400       | 2975539      | 410759      | 23555036        |
+----------+-------------+--------------+--------------+-------------+-----------------+