Set column value when grouped record is null - mysql

Question

I have the following query which returns rows grouped.
For the column mc_name which returns a NULL value, is there any way to set a value without changing records data?
This is the query:
select
megaagents.megaagent_name AS 'mc_name',
SUM(IF(MONTH(properties.created_at) = 1, 1, 0)) as ENE,
SUM(IF(month(properties.created_at) = 2, 1, 0)) AS FEB,
SUM(IF(month(properties.created_at) = 3, 1, 0)) as MAR,
SUM(IF(month(properties.created_at) = 4, 1, 0)) AS ABR,
SUM(IF(month(properties.created_at) = 5, 1, 0)) AS MAY,
SUM(IF(month(properties.created_at) = 6, 1, 0)) as JUN,
SUM(IF(month(properties.created_at) = 7, 1, 0)) as JUL,
SUM(IF(month(properties.created_at) = 8, 1, 0)) AS AGO,
SUM(IF(month(properties.created_at) = 9, 1, 0)) as SEP,
SUM(IF(month(properties.created_at) = 10, 1, 0)) as OCT,
SUM(IF(month(properties.created_at) = 11, 1, 0)) as NOV,
SUM(IF(month(properties.created_at) = 12, 1, 0)) as DIC,
COUNT(PROPERTIES.PROP_EXCLUSIVE) AS TOTAL
from
`properties`
left join `megaagents` on `properties`.`megaagent_id` = `megaagents`.`id`
where
`properties`.`marketcenter_id` = 11
and `properties`.`prop_exclusive` in ('No Exclusiva', 'Exclusiva')
and `properties`.`prop_transaction` in ('Alquiler Temporal', 'Alquiler', 'Venta')
group by
`megaagents`.`megaagent_name`
order by
`megaagents`.`megaagent_name` asc
Regards!

Answer 1

Use COALESCE():
select
coalesce(megaagents.megaagent_name, 'custom value') AS mc_name,
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