C# 从固件FW1中选择FW1.id，计数（*）。将固件FW2连接到FW1上。固件_组_id=FW2。固件_组_id和FW1.br_日期

---

从固件FW1中选择FW1.id，计数（*）。将固件FW2连接到FW1上。固件_组_id=FW2。固件_组_id和FW1.br_日期FW1.br_date，你会怎么做？你怎么翻译这个？@copoolse，我已经尝试过了，但对我不起作用。我很感激你的想法。但是我正在寻找Linq中的自我连接，并比较t。）他用更少的字符串来表示日期（只是出于好奇：如果在本期中有一个像这样的左连接，但在连接条件中只有条件

FW1.br_date

，你会怎么做？如何翻译？

SELECT 
    FW1.id, count(*) 
FROM 
    firmware FW1 
LEFT JOIN
    firmware FW2 ON FW1.firmware_group_id = FW2.firmware_group_id
                 AND FW1.br_date < FW2.br_date 
                 AND FW2.[public]= '1'  
GROUP BY
    FW1.id

from f1 in firmwares
from f2 in firmwares
let f1_date = DateTime.Parse(f1.Dt)
let f2_date = DateTime.Parse(f2.Dt)
where f1.Group_Id == f2.Group_Id && f1_date < f2_date
group f1 by f1.Id into fres
select new {
    Id = fres.Key,
    Count = fres.Count()
};

var result = FW1.GroupJoin(FW2,      // GroupJoin FW1 and FW2
    fw1 => fw1.firmware_group_id,    // from fw1 take the primary key firmware_group_id
    fw2 => fw2.firmware_group_id,    // from fw2 take the foreing key firmware_group_id

    (fw1, fw2s) => new               // from every fw1, with all its matching fw2s 
    {                                // make one new object containing the following properties:
        Id = fw1.Id,

        // Count the fw2s of this fw1 that have public == 1
        // and a date larger than fw1.date
        Count = fw2.Where(fw2 => fw2.Public == 1 && fw1.br_date < fw2.br_date)
                   .Count(),         
    });