Hello

I have a table that contains a column CALL_START which is a Timestamp.
I'd like to display a graph showing when calls arrived, grouped into
user definable 'buckets'. i.e. the user can selct 5m, 10m, 15m, 20
etc.

Thus far I have:

select CALL_START,
CAST(CAST(CALL_START - CAST('12/04/2004' AS TIMESTAMP) AS double
precision) / 0.01041666666666666 as Integer )
from calls
where CALL_START >= '12/04/2004' AND CALL_START <= '12/05/2004'


NB: 0.01041666666666666 is a 15min period [ 15/(60 x 24) ]

This lists the call start and also which 'bucket' the call belongs in,
but I need to count how many calls are in each bucket and output the
data like this:

Bucket No, Bucket count
1 5
2 12
3 45
4 22
etc

I cannot seem to group by a 'CAST' column, e.g.

select CAST(CAST(CALL_START - CAST('12/04/2004' AS TIMESTAMP) AS
double precision) / 0.01041666666666666 as Integer ),
count( CAST(CAST(CALL_START - CAST('12/04/2004' AS TIMESTAMP) AS
double precision) / 0.01041666666666666 as Integer ) )
from calls
where CALL_START >= '12/04/2004' AND CALL_START <= '12/05/2004'
group by CAST(CAST(CALL_START - CAST('12/04/2004' AS TIMESTAMP) AS
double precision) / 0.01041666666666666 as Integer )

This fails with token unknown 'CAST' on the group by line.

Naming the first cast 'AS BucketNum' and then doing 'group by
BucketNum' fails, with FB failing to recognise 'BucketNum'

Any ideas?

Thanks

David