Question

我有一个EF查询，其中包含许多聚合子查询（Count，Sum和Max）。有两个问题。

我需要将子查询的连接保留为连接，以便即使聚合子查询中没有结果也会返回记录。目前，只有在所有子查询都返回记录时才会返回记录。
返回的WholesaleCustomerAndAggregateOrders对象的结果列表包含一个需要还包含地址和县的Contact对象。我在查询中添加了Include(c => c.Addresses.Select(a => a.Country))，但Contact对象不包含任何Address对象。

对任何一个问题的任何帮助将不胜感激。完整查询如下。

var month1Date = DateTime.Today.AddMonths(-1);
var month3Date = DateTime.Today.AddMonths(-3);
var month6Date = DateTime.Today.AddMonths(-6);
var month12Date = DateTime.Today.AddMonths(-12);

var db = GetNewContext();
var qry = from c in db.Contacts
                      .Include(c => c.Addresses.Select(a => a.Country))
          join orderCount in
              (
                  from o in db.WholesaleOrders
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalOrders = g.Count()
                  }
              ) on c.Id equals orderCount.ContactId
          join month1Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month1Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month1Value.ContactId
          join month3Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month3Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month3Value.ContactId
          join month6Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month6Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month6Value.ContactId 
          join month12Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month12Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month12Value.ContactId
          join month12Quantity in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month12Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      OrderCount = g.Count()
                  }
              ) on c.Id equals month12Quantity.ContactId
          join lastOrderDate in
              (
                  from o in db.WholesaleOrders
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      LastOrderDate = g.Max(r => r.OrderDate)
                  }
              ) on c.Id equals lastOrderDate.ContactId
          select new WholesaleCustomerAndAggregateOrders
          {
              Contact = c,
              TotalOrders = orderCount.TotalOrders,
              Month1Value = month1Value.TotalValue,
              Month3Value = month3Value.TotalValue,
              Month6Value = month6Value.TotalValue,
              Month12Value = month12Value.TotalValue,
              Month12OrderCount = month12Quantity.OrderCount,
              LastOrderDate = lastOrderDate.LastOrderDate
          };

return await qry.ToListAsync();

Answer 1

这个怎么样：

db.WholesaleOrders
    .GroupBy(o => o.ContactId)
    .Select(a => new { 
        a.Key, 
        TotalOrders = a.Count(),
        LastOrderDate = a.Max(r => r.OrderDate),
        Month1Value = a.Where(b => b.OrderDate >= month1Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price),
        Month3Value = a.Where(b => b.OrderDate >= month3Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price),
        Month6Value = a.Where(b => b.OrderDate >= month6Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price),
        Month12Value = a.Where(b => b.OrderDate >= month12Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price)
        }).ToListAsync();

更新：向投影添加另一个属性：

Addresses = db.Addresses.Where(ad => ad.ContactId == a.Key);

其中db是您的上下文，ad.ContactId是地址表中联系人的FK。

为此，连接的multipleactiveresultsets属性必须设置为True。

实体框架左连接聚合查询

1 个答案: