want resultset grouped by month have only datetime type

[kanchan thukral]

actually i'm using datetime data type in mysql and i want to run the query which return grouped by month resultset

i'm running this querry

select * from alarmlog group by (select month('alarmlog.creationtime'))

here creationtime is datetime datatype.actually month is returning null value.
so the whole table is grouping in only one resultset as month is null

so please tell me.