Mysql hourly report query

Mysql hourly report query

I want to get an hourly report of conversions for all 24 hours. I have
this query but it returns only 19rows instead of 24 can anyone plz tell me
wats wrong in this? Thanks in advance.
SELECT HOUR( `date_time` ) AS Hours, COUNT(conversion_id) AS
`conversion` FROM conversions
RIGHT JOIN (SELECT 0 AS Hour UNION ALL SELECT 1 UNION ALL SELECT 2
UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT
5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION
ALL SELECT 9 UNION ALL SELECT 10 UNION ALL SELECT 11
UNION ALL SELECT 12 UNION ALL SELECT 13 UNION ALL SELECT 14 UNION ALL
SELECT 15 UNION ALL SELECT 16 UNION ALL SELECT 17 UNION ALL
SELECT 18 UNION ALL SELECT 19 UNION ALL SELECT 20 UNION ALL SELECT 21
UNION ALL SELECT 22 UNION ALL SELECT 23) AS AllHours
ON HOUR(date_time) = Hour
WHERE DATE(date_time) = CURDATE() OR date_time IS NULL
GROUP BY Hour
ORDER BY Hour