select day, ad, sum(clicks), sum(impressions)
   from tracking
   where client = 11 and day between '2007-01-01' and '2007-01-31'
   group by day;

select day, ad, sum(clicks), sum(impressions)
   from tracking2
   where client = 11 and day between '2007-01-01' and '2007-01-31'
   group by day;

select day, ad, sum(clicks), sum(impressions)
   from tracking2 use index(primary)
   where client = 11 and day between '2007-01-01' and '2007-01-31'
   group by day;