linq-to-sql - linq to sql 是否有 with ties 选项？

Question

我正在尝试将以下查询移动到 Linq-to-sql，这可能吗？

select * from (
Select top (@Percent) percent with ties *
from(
    Select distinct
      LoanNumber as LoanNo
    From CHE 
    Left Join RecordingInfo as Rec
    On CHE.LoanNumber = Rec.LoanNo
    Where Channel = 'LINX'
        and CHE.Doc in ('MTG','MOD')
        and Rec.LoanNo is null
        and LoanNumber >= '@LoanNo'
) A
order by LoanNo @Order
) B
order by LoanNo

无论如何，我还没有看到与 linq 中的关系有关。

Answer 1

我认为这样的东西对你有用。

public static IQueryable<T> TopPercentWithTies<T, TKey>(this IOrderedQueryable<T> query, Expression<Func<T, TKey>> groupByExpression, double percent)
{
    var groupedQuery = query.GroupBy(groupByExpression);
    int numberToTake = groupedQuery.Count() * percent / 100;
    return groupedQuery.Take(numberToTake).SelectMany(t => t);
}

我只用 IEnumerable 测试过它，所以我不确定它是否能与 IQueryable 一起正常工作。我还在调用 TopPercentWithTies() 之前对列表进行了排序。

这是我用来测试它的代码。

int percent = 50;
var people = new []
{
    new { Age = 99, Name = "Adam" },
    new { Age = 99, Name = "Andrew" },
    new { Age = 89, Name = "Bob" },
    new { Age = 50, Name = "Cecil" },
    new { Age = 50, Name = "Doug" },
    new { Age = 50, Name = "Everett" },
    new { Age = 35, Name = "Frank" },
    new { Age = 25, Name = "Greg" },
    new { Age = 15, Name = "Hank" }
};
var sortedPeople = people.AsQueryable().OrderByDescending(person => person.Age);
var results = sortedPeople.TopPercentWithTies(person => person.Age, percent);
foreach (var person in results)
    Console.WriteLine(person);

希望它对您有所帮助，或者至少让您朝着正确的方向前进。您可能想要调整计算 numberToTake 的逻辑。