Miscellaneous

I will preface this with I am not very good with SQL I understand enough to modify pre-existing statements to fit my need.

I'm looking for any assistance on creating a report that shows the average resolution time for each month. I'm currently using the below SQL but I can't seam to figure out how to get the average time for each month.

SELECT
(case
    when TIME_CLOSEDDATE_ADD(IF(TIME_OPENED='0',TIME_CLOSED,TIME_OPENED),INTERVAL 24 HOUR) then '>24 hours'
    else 'error' end ) as CLOSE_GROUP,
count(HD_TICKET.ID) as NUMBER_OF_TICKETS,
CONCAT((sum(TIME_TO_SEC(TIMEDIFF(TIME_CLOSED,IF(TIME_OPENED='0',TIME_CLOSED,TIME_OPENED))))/count(HD_TICKET.id)
div 86400),'d ',
TIME_FORMAT(SEC_TO_TIME(sum(TIME_TO_SEC(TIMEDIFF(TIME_CLOSED,IF(TIME_OPENED='0',TIME_CLOSED,TIME_OPENED))))/count(HD_TICKET.id) mod 86400 ), '%kh %im %ss')) as AVG_TIME_TO_CLOSE from HD_TICKET,
HD_STATUS
where
HD_TICKET.HD_STATUS_ID=HD_STATUS.ID
and HD_STATUS.NAME='Closed'
and TIME_CLOSED<>0
and TIME_CLOSED> (curdate() - interval 1 month) /*change the start date here*/
and HD_TICKET.HD_QUEUE_ID in (1) /*add queue numbers here*/
group by CLOSE_GROUP
UNION
select 'all' as CLOSE_GROUP,count(HD_TICKET.ID) as NUMBER_OF_TICKETS,
CONCAT((sum(TIME_TO_SEC(TIMEDIFF(TIME_CLOSED,IF(TIME_OPENED='0',TIME_CLOSED,TIME_OPENED))))/count(HD_TICKET.id)
div 86400),'d ',
TIME_FORMAT(SEC_TO_TIME(sum(TIME_TO_SEC(TIMEDIFF(TIME_CLOSED,IF(TIME_OPENED='0',TIME_CLOSED,TIME_OPENED))))/count(HD_TICKET.id)
mod 86400 ), '%kh %im %ss')) as AVG_TIME_TO_CLOSE from HD_TICKET
,HD_STATUS
where
HD_TICKET.HD_STATUS_ID=HD_STATUS.ID
and HD_STATUS.NAME='Closed'
and TIME_CLOSED<>0
and TIME_CLOSED> (curdate() - interval 1 month) /*change the start date here*/
and HD_TICKET.HD_QUEUE_ID in (1) /*add queue numbers here*/
group by CLOSE_GROUP

I've tried adding this case statement with the others but not having any luck.

when TIME_CLOSED between '2022-01-01 14:15:55' and '2022-01-31 14:15:55' then 'January'