Få summen af ​​en værdi for to separate datointervaller i samme kolonne og i en enkelt MySQL-forespørgsel

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select a.date,sum(b.qty * b.price) As sum from sales As a, product As b where DATE_FORMAT(a.date,'%d-%m-%Y') between '27-05-2014' AND '28-05-2014' and a.id_sale=b.id_sale group by a.date