Detta får inte datum med nollor, för det behöver du antingen en datumtabell eller en lagrad procedur för att gå igenom datum. Ett sätt att göra det är ett underval från en fackföreningsfråga (otestad):
SELECT commission_date, SUM(click_commission), SUM(lead_commission), SUM(total_commission)
FROM (SELECT DATE(click.time) AS commission_date, click.commission AS click_commission,
0 AS lead_commission, click.commission AS total_commission
FROM click
UNION ALL
SELECT DATE(lead.time) AS commission_date, 0 AS click_commission,
lead.commission AS lead_commission, lead.commission AS total_commission
FROM lead) AS foo
GROUP BY commission_date
ORDER BY commission_date