如何使用 LINQ 或 HQL 执行以下 SQL 查询

Question

如何使用 Castle ActiveRecords 和 LINQ 或 HQL 执行以下查询？

选择 a.id、s.classes、COUNT(p.id)、MAX(p.date) 作为最后一个、MIN(p.date) 作为第一个
来自帐户 a
左加入学校 s.account_id = a.id
LEFT JOIN 用户 u ON u.account_id = a.id
LEFT JOIN 点 p ON p.user_id = u.id
付款方式=“S”
按 a.id 分组

这些表按以下方式关联：

我还为所有定义了正确关系的表提供了 ActiveRecord 类（如果我按步骤进行查询，它可以工作） ，但速度很慢，因为有很多行），我尝试了以下方法，但没有成功：

var result = from account in AccountRecord.Queryable
             join s in SchoolRecord.Queryable on account equals s.Account into schools
             from school in schools.DefaultIfEmpty(null)
             join user in UserRecord.Queryable on account equals user.Account
             join p in PointsRecord.Queryable on user equals p.User into points
             where account.PaymentType == "S"
             select new { Account = account, School = school, Count = points.Count() };

抛出以下 The method or opera is not Implement-Exception at:

NHibernate.Linq.Visitors.QueryModelVisitor.VisitGroupJoinClause(GroupJoinClause groupJoinClause, QueryModel queryModel, Int32 索引)

Answer 1

使用 HQL 找到了解决方案 - 我仍然愿意使用 LINQ 解决方案：

HqlBasedQuery query = new HqlBasedQuery(typeof(AccountRecord),
    "SELECT a, s, COUNT(p), MIN(p.DateUTC), MAX(p.DateUTC) " +
    "FROM AccountRecord a " +
    "LEFT JOIN a.Schools s " +
    "LEFT JOIN a.Users u " +
    "LEFT JOIN u.Points p " +
    "WHERE a.PaymentType=:payment GROUP BY a.Id");
query.SetParameter("payment", "S");
var result = from object[] row in (ArrayList)ActiveRecordMediator.ExecuteQuery(query)
                select new
                {
                    Account = row[0] as AccountRecord,
                    School = row[1] as SchoolRecord,
                    Count = row[2],
                    First = (new DateTime(1970, 1, 1, 0, 0, 0, 0)).AddSeconds(Convert.ToDouble(row[3])),
                    Last = (new DateTime(1970, 1, 1, 0, 0, 0, 0)).AddSeconds(Convert.ToDouble(row[4]))
                };

Answer 2

我认为您的 Linq 查询类似于：

var result = from a in AccountRecord.Queryable
             join s in SchoolRecord.Queryable on a.id equals s.account_id
             join u in UserRecord.Queryable   on a.id equals u.account_id
             join p in PointsRecord.Queryable on u.id equals p.user_id
             where a.payment == "S"
             group by a.id
             select new
             {
               Account = a,
               School = s,
               Count = p.Count()
             };

尽管我不确定 NHibernate 处理 group by 和 Count() 组合的效果如何。您可能想看看生成的 SQL 最终会是什么（如果它没有抛出错误）。

如果这不起作用，您可能需要选择回记录，然后在应用程序中对它们进行分组/计数，更像是：

var data = from a in AccountRecord.Queryable
           join s in SchoolRecord.Queryable on a.id equals s.account_id
           join u in UserRecord.Queryable   on a.id equals u.account_id
           join p in PointsRecord.Queryable on u.id equals p.user_id
           where a.payment == "S"
           select new
           {
             Account = a,
             School = s,
             Count = c
           };
var grouped = data.ToList.GroupBy(x => x.Account.Id);