我正在尝试使用 LINQ 创建查询到实体,以计算产品评级的平均值。在订购评级之前,我将每个产品的平均值投影到匿名对象。然后,我只想获取结果的一部分。
查询如下:
var query = Items.GroupBy(review => review.Product)
.Select(group => new
{
Product = group.Key,
Rating = group.Average(review => review.Rating)
})
.OrderByDescending(pr => pr.Rating)
.Skip(itemsToSkip)
.Take(count)
.ToList();
生成的查询如下所示:
{SELECT
1 AS [C1],
[GroupBy1].[K1] AS [ProductId],
[GroupBy1].[K2] AS [TotalImages],
[GroupBy1].[K3] AS [TotalVideos],
[GroupBy1].[K4] AS [TotalAudioRecordings],
[GroupBy1].[K5] AS [Name],
[GroupBy1].[K6] AS [DiscountedPrice],
[GroupBy1].[K7] AS [Status],
[GroupBy1].[A1] AS [C2]
FROM ( SELECT
[Extent2].[ProductId] AS [K1],
[Extent2].[TotalImages] AS [K2],
[Extent2].[TotalVideos] AS [K3],
[Extent2].[TotalAudioRecordings] AS [K4],
[Extent2].[Name] AS [K5],
[Extent2].[DiscountedPrice] AS [K6],
[Extent2].[Status] AS [K7],
AVG([Extent1].[Rating]) AS [A1]
FROM [dbo].[ProductReviews] AS [Extent1]
LEFT OUTER JOIN [dbo].[Products] AS [Extent2] ON [Extent1].[Product_ProductId] = [Extent2].[ProductId]
GROUP BY [Extent2].[ProductId], [Extent2].[TotalImages], [Extent2].[TotalVideos], [Extent2].[TotalAudioRecordings], [Extent2].[Name], [Extent2].[DiscountedPrice], [Extent2].[Status]
) AS [GroupBy1]}
查询无法跳过任何项目或仅获取几个结果。相反,它返回数据库中每个产品的平均值计算。
是否有可能像我试图做的那样利用Skip
和Take
?如果是这样,如何更正查询以获得所需的结果?我希望不要从数据库中提取所有数据。
我认为
您可能需要在查询中添加一个选择:
var query = Items.GroupBy(review => review.Product)
.Select(group => new
{
Product = group.Key,
Rating = group.Average(review => review.Rating)
})
.OrderByDescending(pr => pr.Rating)
.Select(x => new { Product = x.Product, Rating = x.Rating })
.Skip(itemsToSkip)
.Take(count)
.ToList();