[英]Linq query with left join and group
我無法將此SQL查詢轉換為有效的linq語句
select sum(cena), id_auta, max(servis) from dt_poruchy left outer join mt_auta on dt_poruchy.id_auta=mt_auta.id
where dt_poruchy.servis>=3 group by id_auta;
我試過這樣的東西,但我無法處理select語句
var auta = from a in MtAuta.FindAll()
join p in DtPoruchy.FindAll() on a equals p.MtAuta into ap
from ap2 in ap.DefaultIfEmpty()
where ap2.SERVIS >= 3
group ap2 by ap2.ID into grouped
select new {
我會感激任何幫助!
基於提供的有限信息(哪些表是某些字段來自?),這是我想出的。
var auta = from a in MtAuta.FindAll()
let p = a.DtPoruchys.Where(s => s.SERVIS >= 3)
select new
{
Id = a.Id,
CenaSum = p.Sum(c => c.Cena),
Servis = p.Max(s => s.SERVIS)
};
我不確定哪個表格cena和servis來自哪個,但創建分組總和你做的事情。
select new { Sum = grouped.Sum( x => x.cena ) }
並獲得最大
select new { Max = grouped.Group.Max( x => x.servis ) }
這是一個很好的參考。
我已經達到了這個解決方案(假設“cena”屬於MtAuta.FindAll()
):
var auta = from e in
(from a in DtPoruchy.FindAll()
where a.SERVIS >= 3
join p in MtAuta.FindAll() on a.MtAuta equals p.Id into ap
from ap2 in ap.DefaultIfEmpty()
select new
{
Cena = ap.cena,
IdAuta = a.MtAuta,
Servis = a.servis
})
group e by e.IdAuta into g
select new
{
Cena = g.Sum(e => e.cena),
IdAuta = g.Key,
Servis = g.Max(e => e.servis)
};
我已經修改了你的解決方案,我得到它像這樣工作:
var auta = from jo in
(
from a in MtAuta.FindAll()
join p in DtPoruchy.FindAll() on a equals p.MtAuta into ap
from ap2 in ap.DefaultIfEmpty()
where ap2.SERVIS >= 3
select new
{
Cena = ap2.CENA,
Idauto = ap2.ID_AUTA,
Servis = ap2.SERVIS
}
)
group jo by jo.Idauto into g
select new
{
Cena = g.Sum(jo => jo.Cena),
IdAuto = g.Key,
Servis = g.Max(jo => jo.Servis)
};
我只是好奇這是否是最佳解決方案?
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