排行。 Linq 到 sql 问题

发布于 2024-09-06 18:42:40 字数 390 浏览 1 评论 0原文

我有一个由人员发出的订单表：

Orders
{ 
  Guid  PersonId, 
  int   Priority, 
  Guid  GoodId 
}

优先级是某个整数。例如：

AlenId   1  CarId
DianaId  0  HouseId
AlenId   3  FoodId
DianaId  2  FlowerId

我想检索每个人的最高优先级顺序：

AlenId   1  CarId
DianaId  0  HouseId

在 T-SQL 中我将使用排名，如何在 Linq-2-Sql 中获得相同的结果？

先感谢您！

原文

I have a table of orders made by persons:

Orders
{ 
  Guid  PersonId, 
  int   Priority, 
  Guid  GoodId 
}

Priority is some integer number. For example:

AlenId   1  CarId
DianaId  0  HouseId
AlenId   3  FoodId
DianaId  2  FlowerId

I want to retrieve highest priority orders for each person:

AlenId   1  CarId
DianaId  0  HouseId

In T-SQL I'll use ranking, how can I get the same result in Linq-2-Sql ?

Thank you in advance!

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甜是你 2024-09-13 18:42:40

像这样的事情：

var query = from order in context.Orders
            orderby order.Priority
            group order by order.PersonId into personOrders
            select personOrders.First();

我相信应该有效，但我不知道它在分组后排序方面的定义有多明确。这也可以工作，尽管它有点难看：

var query = from order in context.Orders
            group order by order.PersonId into personOrders
            select personOrders.OrderBy(order => order.Priority).First();

或者只使用点表示法：

var query = context.Orders
                   .GroupBy(order => order.PersonId)
                   .Select(group => group.OrderBy(order => order.Priority)
                                         .First());

Something like this:

var query = from order in context.Orders
            orderby order.Priority
            group order by order.PersonId into personOrders
            select personOrders.First();

I believe that should work, but I don't know how well-defined it is, in terms of the ordering post-grouping. This would also work, although it's slightly uglier:

var query = from order in context.Orders
            group order by order.PersonId into personOrders
            select personOrders.OrderBy(order => order.Priority).First();

Or using just dot notation:

var query = context.Orders
                   .GroupBy(order => order.PersonId)
                   .Select(group => group.OrderBy(order => order.Priority)
                                         .First());

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