sql - 将 SQL join 与 group by 和 MAX 转换为 Linq

Question

我在 sql 中创建了以下查询，但我无法找出如何在我的 linq 中实现 StatusAndTrackingNotes 表连接：

SELECT *
FROM [Application] APP
join User USR on APP.ApplicationId = USR.UserApplicationId
join 
(Select MAX(TrackingDate) as MaxDateTD,TrackingApplicationId
 From StatusAndTrackingNotes 
 where TrackingLoanType = 1 and ((TrackingStatusCode <= 52 and TrackingStatusCode >= 50) or TrackingStatusCode = 62)
 group by TrackingApplicationId) MTND on APP.ApplicationId = MTND.TrackingApplicationId
join Details DTL on APP.ApplicationId = DTL.ApplicationId
join ApplicationFees AF on APP.ApplicationId = AF.ApplicationId
where APP.LatestStatus = 'F' and DTL.Type = 1 and DTL.FundingDate >= '2011-06-01'  and   DTL.FundingDate <= '2013-06-30'
    and AF.FirstRefPaidDate is not null

请帮助我使用语法。首先我使用简单的查询和连接，然后

([Linq Query]).GroupBy(i => i.TrackingApplicationId).Select(g => g.OrderByDescending(c => c.TrackingDate).FirstOrDefault());

但它不返回任何结果。请帮忙。提前致谢

Answer 1

我会通过创建StatusAndTrackingNotes单独的查询并将其加入并将其分组到“主查询”来解决它。IE：

var trackingQuery =
    from t in statusAndTrackingNotes
    where t.TrackingLoanType == 1 && (t.TrackingStatusCode <= 52 && t.TrackingStatusCode >=50) || t.TrackingStatusCode == 62
    group t by t.TrackingApplicationId into trackings
    select new 
    { 
        TrackingApplicationId = trackings.Key,
        MaxDate = trackings.Max(t => t.TrackingDate)
    };

var appQuery =
    from app in Application
    join t in trackingQuery on app.ApplicationId equals t.TrackingApplicationId
    /* other joins here */
    select new
    {
        app,
        t.MaxDate,
    };