[英]Linq group by, orderbydescending, and count
因此,我正在尝试执行linq语句来对两个数据库表进行分组,并根据每个类别的评论数来选择前25个表。 所以我的sql语句是
SELECT TOP 25 BusinessCategories.Category, COUNT(*) as count
FROM Reviews
JOIN BusinessCategories
ON BusinessCategories.BusinessID=Reviews.BusinessID
GROUP BY BusinessCategories.Category
ORDER BY count desc
哪个完美。 因此,现在尝试在我的网络API中执行此操作时遇到了麻烦。 这就是我所拥有的:
var top = (from review in Db.Reviews
from category in Db.BusinessCategories
where review.BusinessID == category.BusinessID
group review by category into reviewgroups
select new TopBusinessCategory
{
BusinessCategory = reviewgroups.Key,
Count = reviewgroups.Count()
}
).OrderByDescending(x => x.Count).Distinct().Take(25);
这给了我一些相同的结果,但是看起来当我在浏览器中调用api时,所有计数都是相同的...所以我做错了什么。
试试这个可能对你有用
var top = (from review in Db.Reviews
join category in Db.BusinessCategories
on review.BusinessID equals category.BusinessID
group review by category into reviewgroups
select new TopBusinessCategory
{
BusinessCategory = reviewgroups.Key,
Count = reviewgroups.Key.categoryId.Count() //CategoryId should be any
//property of Category or you
//can use any property of category
}).OrderByDescending(x => x.Count).Distinct().Take(25);
使用此解决问题
[HttpGet]
[Queryable()]
public IQueryable<TopBusinessCategory> GetTopBusinessCategories()
{
var top = (from p in Db.BusinessCategories
join c in Db.Reviews on p.BusinessID equals c.BusinessID into j1
from j2 in j1.DefaultIfEmpty()
group j2 by p.Category into grouped
select new TopBusinessCategory
{
BusinessCategory = grouped.Key,
Count = grouped.Count(t => t.BusinessID != null)
}).OrderByDescending(x => x.Count).Take(25);
return top.AsQueryable();
}
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