在 sql 中编写一个类似的 LINQ 查询来聚合非重复计数？

Question

我想获得每个月的计数，但即使发生多次，计数也只能每天最多一次。我的 SQL 查询可以正常工作，但无法将其转换为 LINQ -

select 
    count(DISTINCT DAY(date)) as Monthly_Count,
    MONTH(date) as Month,
    YEAR(date)
from 
    activity
where 
    id=@id
group by
    YEAR(date),
    MONTH(date) 

谁能帮我将上述查询转换为 LINQ。谢谢！

Answer 1

根据 使用 GROUP BY 和 COUNT(DISTINCT) 的 LINQ to SQL由@Rick给出，这应该有效：

var query = from act in db.Activity
            where act.Id == id
            group act by new { act.Date.Year, act.Date.Month } into g
            select new
            {
                MonthlyCount = g.Select(act => act.Date.Day).Distinct().Count(),
                Month = g.Key.Month,
                Year = g.Key.Year
            };

我不知道L2S是否可以转换内部g.Select(act =>; act.Date.Day).Distinct.Count() 正确。

Answer 2

var results = db.activities.Where(a => a.id == myID)
                           .GroupBy(a => new 
                                         {
                                             Month = a.date.Month, 
                                             Year = a.date.Year
                                         })
                           .Select(g => new
                                        {
                                            Month = g.Key.Month,
                                            Year = g.Key.Year,
                                            Monthly_Count = g.Select(d => d.date.Day)
                                                             .Distinct()
                                                             .Count()
                                        })