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给定下表：

仪器日志

InstrumentLogId (PK, int, not null)
InstrumentId (FK, int, not null)
LogDate (datetime, not null)
Action (string, not null)

仪器

InstrumentId (PK, int, not null)
CountyId (FK, int, not null)

县

CountyId (PK, int, not null)
StateFips (FK, int, not null)
Name (string, not null)

状态

StateFips (PK, int, not null)
Name (string, not null)

我需要弄清楚如何使用实体框架编写这个 SQL 查询：

select s.StateName, count(*) as total
from instruments as i 
join counties as c on i.CountyID = c.CountyID
join states as s on s.StateFIPS = c.StateFIPS
where i.InstrumentID in 
   (select i1.InstrumentId from InstrumentLogs as i1 where i1.action = 'review' and
    i1.logdate in (select max(logdate) from instrumentlogs as i2 where i1.instrumentid 
    =i2.InstrumentID group by i2.instrumentid))
group by s.StateName

我尝试了一些类似的东西：

_context.Instruments.Include(i => i.County.State)
  .Where(i => _context.Logs.Where(l => l.Action == 'review' 
     && _context.Logs.Where(l2 => l2.InstrumentId == l.InstrumentId).Max(l2 => l2.LogDate) == l.LogDate).GroupBy(i => i.County.State.Name)
  .Select(g => new { State = g.Key.Name, Total = g.Count() });

但是，EF 不喜欢这样。我以错误告终，指出仅支持原始类型或枚举类型。

谢谢你的帮助。

4

1 回答 1

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我终于让它像这样工作了

        var _query = _dataContext.IndexLogs.GroupBy(l => l.InstrumentId, l => l)
            .Select(grp => new { Id = grp.Key, Date = grp.Max(g => g.ActionDate) });

        //Prequery to find log records that match given type and action type
        var _indexes = _dataContext.IndexLogs.Where(l => l.Action == type 
            && _query.Contains(new { Id = l.InstrumentId, Date = l.ActionDate})).Select(i => i.InstrumentId);


        var _states = _dataContext.AdvancedIndexes
            .Include(i => i.County.State)
            .Where(a => a.Id > 0 && _indexes.Contains(a.Id))
            .GroupBy(i => new { i.County.State.Id, i.County.State.Name })
            .Select(g => new { fips = g.Key.Id, name = g.Key.Name, count = g.Count() });
于 2013-05-04T20:01:18.730 回答