c# - 获取日期之间最畅销的 10 种产品

Question

我想在用户指定的日期内退回前 10 名最畅销的产品（数量最多）。

我来自数据库的表：

订单

OrderId | OrderDate

订购_产品：

ProductID | OrderID | Quantity

产品

ProductID | ProductName | ProductDescription

代码：

return (from product in this.Entities.Products
        from orderProduct in this.Entities.Order_Product 
        from order in this.Entities.Orders
        where order.OrderId = orderProduct.ProductID && orderProduct.ProductID == product.ProductID
        where (order.OrderDate >= date1 &&  <= date2)
        select product).OrderByAscending(COUNT(Quantity)).Distinct().Take(10);

代码到现在。

Answer 1

我可以想到两种方法来做到这一点

这会对每个产品进行子查询，以总结日期范围之间的销售数量。这对我来说似乎最清楚，但可能表现不佳

  var query = 
   (from p in Entities.Products
    let totalQuantity = ( from op in Entities.Order_Product
                          join o in Entities.Orders on op.OrderID equals o.OrderId
                          where op.ProductID == p.ProductID && o.OrderDate >= date1 && o.OrderDate <= date2
                          select op.Quantity ).Sum()
    where totalQuantity > 0
    orderby totalQuantity descending
    select p).Take(10);

或者作为单个查询获取日期范围内的所有订单，按产品对它们进行分组，并对数量求和。

  var query = 
   (from p in Entities.Products
    join op in Entities.Order_Product on p.ProductID equals op.ProductID
    join o in Entities.Orders on op.OrderID equals o.OrderId
    where o.OrderDate >= date1 && o.OrderDate <= date2
    select new { Product = p, Quantity = op.Quantity } into productQty
    group productQty by productQty.Product into pg
    let totalQuantity = pg.Sum(prod => prod.Quantity)
    orderby totalQuantity descending
    select pg.Key).Take(10);

Answer 2

var query = 
   (from p in Entities.Products
    join op in Entities.Order_Product on p.ProductID equals op.ProductID
    join o in Entities.Orders on op.OrderID equals o.OrderId
    where o.OrderDate >= date1 && o.OrderDate <= date2
    select new { Product = p, op.Quantity } into pq
    group pq by pq.Product.ProductID into g
    select g.OrderByDescending(x => x.Quantity).First().Product).Take(10);