[Koha] Report Help

I am looking at this report in the report library: SELECT DATE(datetime) AS date, substring(itemcallnumber,1,1) AS 'Call# range', count(*) AS count FROM statistics LEFT JOIN items USING (itemnumber) WHERE statistics.type IN ('issue', 'renew') AND YEAR(datetime) = 2010 GROUP BY DATE(datetime), substring(itemcallnumber,1,1) And I'm wondering if anyone knows how I could change that substring bit to show me everything before the first space. For example I want F but I also want JFIC - basically I want to lump it together using the first bit of the call number - the bit before the space. Thanks in advance, Nicole