我的实体结构如下：

public class DisbursementItem
{
    public int DisbursementNumber;
    public int IDDisbursementItem;
    public int IDReceiptItem;
    public decimal Amount;
    public decimal MeasureUnit;
    public decimal PricePerMU;
    public decimal PriceTotal;
    public Disbursement Disbursement_IDDisbursement;
    public int IDDisbursementNumber;
}

public class Disbursement
{
    public int DisbursementNumber;
    DateTime date;
    DisbursementType DType;
    string Note;
    string Subscriber;
    Subscriber SubscriberModel;
    string ItemType;
    int ProcessNumber;
}

public class Subscriber 
{
    public string Name
    public string Address;
    public string City;
}

public class DisbursementDescription
{
    public int IDDisbursementItem;
    public string Description;
}

public class Receipt
{
    public int IDReceiptItem;
    public int ItemNumber;
}

public class StorageCard 
{
    public int ItemNumber;
    public string StorageCardGroup;
    public string StorageCardName;
}

我的 EF6 LINQ 查询是：

DateTime from;
DateTime to;
var result = context.DisbursementItem
    .Where(x => x.Disbursement_IDDisbursement.Date <= to && x.Disbursement_IDDisbursement.Date >= from)
    .Join(context.DisbursementDescription, di => di.IDDisbursementItem, dd => dd.IDDisbursementItem, (di, dd) => new {di = di, desc = dd.Description})
    .Join(context.Receipt, x => x.di.IDReceiptItem, r => r.IDReceiptItem, (x, r) => new { di = x.di, desc = x.desc, r = r })
    .Join(context.StorageCard, x => x.r.ItemNumber, sc => sc.ItemNumber, (x, sc) => new { di = x.di, desc = x.desc, r = x.r, sc = sc})
    .GroupBy(g => new {g.di.DisbursementNumber, g.sc.ItemNumber, g.di.MeasureUnit})
    .Select(x => new
    {
        Date = x.FirstOrDefault().di.Disbursement_IDDisbursement.Date,
        DisbursementNumber = x.Key.DisbursementNumber,
        DType = x.FirstOrDefault().di.Disbursement_IDDisbursement.DType,
        Note = x.FirstOrDefault().di.Disbursement_IDDisbursement.Note,
        Subscriber = x.FirstOrDefault().di.Disbursement_IDDisbursement.Subscriber,
        SubscriberName = x.FirstOrDefault().di.Disbursement_IDDisbursement.SubscriberModel.Name,
        SubscriberAddress = x.FirstOrDefault().di.Disbursement_IDDisbursement.SubscriberModel.Address,
        SubscriberCity = x.FirstOrDefault().di.Disbursement_IDDisbursement.SubscriberModel.City,
        ItemNumber = x.FirstOrDefault().sc.ItemNumber,
        StorageCardGroup = x.FirstOrDefault().sc.StorageCardGroup,
        StorageCardName = x.FirstOrDefault().sc.StorageCardName,
        Amount = x.Sum(y => y.di.Amount),
        PricePerMU = x.FirstOrDefault().di.PricePerMU,
        PriceTotal = x.Sum(y => y.di.PriceTotal),
        MeasureUnit = x.Key.MeasureUnit
        Desc = x.FirstOrDefault().desc,
    })
SELECT
    di.Date,
    di.DisbursementNumber,
    d.DType,
    d.Note,
    d.Subscriber,
    subs.Name,
    subs.Address,
    subs.City,
    sc.ItemNumber,
    sc.StorageCardGroup,
    sc.StorageCardName,
    Sum(di.Amount) as Amount,
    di.PricePerMU,
    Sum(di.PriceTotal) as PriceTotal,
    di.MeasureUnit,
    dd.Description

FROM
    DisbursementItem as di

INNER JOIN Disbursement as d 
ON di.IDDisbursementNumber = d.DisbursementNumber

INNER JOIN Receipt as r 
ON di.IDReceiptItem = r.IDReceiptItem

INNER JOIN StorageCard as sc
ON r.ItemNumber = sc.ItemNumber

INNER JOIN DisbursementDescription dd 
ON di.IDDisbuzrsementItem = dd.IDDisbursementItem

WHERE 
    di.Date <= ... and di.Date >= ...

GROUP BY
di.DisbursementNumber, sc.ItemNumber, di.MeasureUnit

这就是我想在 EF 中实现的 SQL 查询

对于几百行，此查询可能需要一分钟多的时间。我该如何优化它？我怀疑多重连接是一个问题，也许也是Sum某些领域的问题。

也不能修改数据库模式。

它产生的查询是巨大的。这就像 SELECT in SELECT in SELECT 一样 40 次。