计算第一次购买时间
CALCULATE(FIRSTDATE(FactInternetSales[OrderDate]),ALLEXCEPT(FactInternetSales,FactInternetSales[CustomerKey]))
添加一个计算列，如果是第一次购买则为New，反之为Old
IF([OrderDate]<=CALCULATE(FIRSTDATE(FactInternetSales[OrderDate]),ALLEXCEPT(FactInternetSales,FactInternetSales[CustomerKey])),"New","Old")