I have the following query in MSSQL:
select TRANSACTION_TYPE_ID ,COUNT(TRANSACTION_TYPE_ID)AS NUMBER_OF_TRANSACTIONS ,CAST(SUM(AMOUNT)AS DECIMAL (30,2)) AS TOTA
Based on Randolph Potter's answer, you can find the average time like:
avg(DATEPART(hh,created_on)*60 + DATEPART(mi,created_on)) % 24 as AvgHour, avg(DATEPART(hh,created_on)*60 + DATEPART(mi,created_on)) / 24 as AvgMinute