SELECT calendar.datefield AS DATE,
       IFNULL(COUNT(digital_lead.id),0) AS leads
FROM digital_lead RIGHT JOIN calendar ON (DATE(digital_lead.received) = calendar.datefield)
WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE('2014-09-01')) FROM digital_lead) AND (SELECT MAX(DATE(received)) FROM digital_lead))
GROUP BY DATE

DATE         LEADS
'2014-11-06', '0'
'2014-11-07', '0'
'2014-11-08', '0'
'2014-11-09', '0'
'2014-11-10', '0'
'2014-11-11', '0'
'2014-11-12', '524'
'2014-11-13', '934'
'2014-11-14', '524'
'2014-11-15', '452'
'2014-11-16', '460'
'2014-11-17', '492'
'2014-11-18', '60'

clock

hours
'00:00:00'
'01:00:00'
'02:00:00'
'03:00:00'
'04:00:00'
'05:00:00'
'06:00:00'... etc

'23:00:00'