谁能帮我将 SQL 转换为 linq 查询。我试过但失败了

Question

这是我的 SQL 查询在 SQL 中运行良好：

select ld.FolderId, count(ld.LeadId) LeadID, sum(note.noteCount) NoteCount, count(ld.CallResultId) Calls 
from LeadsDetails ld 
    left join 
    (
        select lnh.LeadId, Count(lnh.NoteId) as noteCount 
        from [dbo].[LeadNoteHistory] lnh 
        group by lnh.LeadId
    )note
    on note.LeadId=ld.LeadId 
group by ld.FolderId

我试过了-

var query = 
    from lead in _context.LeadsDetails
    join note in _context.LeadNoteHistories
    on lead.LeadId equals note.LeadId into g
    from notes in g.DefaultIfEmpty()
    group lead by lead.FolderId into grp
    select new
    {
        FolderId = g.FolderId,
        LeadID = g.LeadId,
        NoteCount = notes.NoteId,
        Call = lead.CallResultId
    };

无法得到正确的结果。请告诉我做错了什么。

Answer 1

您以后不能在 select 子句中访问变量“g”。您需要使用变量“grp”。您还需要修改最终分组依据。我尝试修改，看看是否可行：

var query = 
    from lead in _context.LeadsDetails
    join note in _context.LeadNoteHistories
    on lead.LeadId equals note.LeadId into g
    from notes in g.DefaultIfEmpty()
    group new {lead,notes} lead by lead.FolderId into grp
    select new
    {
        FolderId = grp.Key,
        LeadID = grp.Count(),
        NoteCount = grp.Count(x=>x.notes!=null),
        Call = grp.Count()
    };

Answer 2

用于将 SQL 转换为 LINQ，

1. 将子选择翻译为单独的变量

2. 按 LINQ 子句顺序翻译每个子句，将单元运算符（DISTINCT、TOP 等）作为应用于整个 LINQ 查询的函数。

3. 使用表别名作为范围变量。使用列别名作为匿名类型字段名称。

4. 对多个列使用匿名类型 (new { })

5. 使用连接变量模拟左连接，然后从连接变量执行另一个from，后跟.DefaultIfEmpty()。

这是您的 SQL 翻译：

var rightside = from lnh in dbo.LeadNoteHistory
                group lnh by lnh.LeadId into lnhg
                select new { LeadId = lnhg.Key, noteCount = lnhg.Count() };

var ans = from ld in dbo.LeadsDetails
          join note in rightside on ld.LeadId equals note.LeadId into notej
          from note in notej.DefaultIfEmpty()
          group new { ld, note } by ld.FolderId into ldnoteg
          select new {
              FolderId = ldnoteg.Key,
              LeadID = ldnoteg.Select(lng => lng.ld.LeadId).Count(),
              NoteCount = ldnoteg.Select(lng => lng.note.noteCount).Sum(),
              Calls = ldnoteg.Select(lng => lng.ld.CallResultId).Count()
          };

我在您的 SQL 中保留了 LeadID 定义，但这对我来说看起来不正确。