将包含 GROUP BY 的 SQL 服务器查询转换为 NHibernate LINQ

Question

我基本上是在尝试检索按（行）创建日期排序的唯一 GUID 的分页列表。

我已经能够根据 this answer 起草一个似乎对我有用的 SQL 服务器查询，但现在我必须将其转换为 LINQ。

SELECT TOP 15 payment.ClientRef, 
          MAX(payment.CreatedDateUtc)
FROM PaymentTransactionState payment
INNER JOIN OrderState orderstate ON payment.ClientRef = orderstate.ClientRef
WHERE orderstate.UserId = 2 AND 
      payment.PaymentState IN (
        'Rejected',
        'Authorized') 
GROUP BY payment.ClientRef
ORDER BY MAX(payment.CreatedDateUtc) DESC,
         payment.ClientRef

问题是，我无法在 IQueryOver 上应用 GroupBy，我可能缺少适当的语法：

session
    .QueryOver<Payment>()
    .JoinAlias(orderState => orderState.OrderStateEntity, () => orderStateRow)
    .Where(() => orderStateRow.UserId == customer.UserId)
    .WhereRestrictionOn(payment => payment.PaymentState).IsIn(paymentStates)
    .GroupBy(pts => pts.ClientRef)
    .OrderBy(payment => payment.CreatedDateUtc).Desc
    .Skip(pageIndex*pageSize)
    .Take(pageSize)
    .List();

我可能可以在查询语法中进行分组，但我不太确定 Skip & Take 位。

Answer 1

我会这样尝试：

var query = db.PaymentTransactionState 
  .Where( pts => pts.OrderState.UserId == 2 &&
                 new string[] {"Rejected", "Authorized"}.Contains(pts.PaymentState) )
  .GroupBy( pts => pts.ClientRef )
  .OrderByDescending( pts => pts.Max( p => p.CreatedDateUtc))
  .ThenBy( p => p.Key )
  .Take(15);

Answer 2

所以这对我有用：基本上我必须使用 SelectList 而不是 GroupBy；一旦我发现 SelectGroup、SelectMax 和 TransformUsing 很容易解决；

PaymentRow paymentAlias = null;
OrderStateRow orderStateRow = null;

var transactionStateRows = session
    .QueryOver<PaymentRow >()
    .JoinAlias(orderState => orderState.OrderStateEntity, () => orderStateRow)
    .Where(() => orderStateRow.UserId == customer.UserId)
    .WhereRestrictionOn(payment => payment.PaymentState).IsIn(paymentStates)
    .SelectList(list => list
        .SelectGroup(payment => payment.ClientRef).WithAlias(() => paymentAlias.ClientRef)
        .SelectMax(payment => payment.CreatedDateUtc).WithAlias(() => paymentAlias.CreatedDateUtc))
    .TransformUsing(Transformers.AliasToBean<PaymentRow >())
    .OrderBy(payment => payment.CreatedDateUtc).Desc
    .Skip(pageIndex*pageSize)
    .Take(pageSize)
    .List();

我会把它留在这里，以防将来有人发现我的辛劳有用。感谢您的回复。

将包含 GROUP BY 的 SQL 服务器查询转换为 NHibernate LINQ

Converting SQL Server query containing GROUP BY into NHibernate LINQ

sql-server

linq

nhibernate

linq-to-nhibernate