SQLite How to Group results by hours?

I have following SQL command which returns count of some values.

    SELECT COUNT(*) AS DIALS_CNT,  
SUM(CASE WHEN dc.call_result = 'APPT' THEN 1 ELSE 0 END) AS 'APPT_CNT',  SUM(CASE WHEN dc.call_result = 'CONV_NO_APPT' THEN 1 ELSE 0 END) AS 'CONVERS_CNT' ,  
SUM(CASE WHEN dc.call_result = 'CANNOT_REACH' THEN 1 ELSE 0 END) AS 'CANNOT_REACH_CNT'  FROM dialed_calls dc ;

I would like to get results grouped by hours to get result like this

--------------------------------------------------
HOUR | APPT_CNT | CONV_NO_APPT | CANNOT_REACH_CNT
--------------------------------------------------
8:00 | 10       | 20           | 30
--------------------------------------------------
9:00 | 20       | 10           | 10
--------------------------------------------------

Etc..to get values for hours where are values higher than zero.

Structure of the table is below:

I suppose that simple usage of the group and having will not be good solution.?

Many thanks for any advice.