如何将sql union转换为linq [英] how to convert sql union to linq

问题描述

我有以下使用联合的Transact SQL查询. 我需要一些关于在LINQ中的外观的指针，例如一些示例 会很好，或者如果有人可以在linq上推荐有关UNIONS的好教程.

I have the following Transact SQL query using a union. I need some pointers as to how this would look in LINQ i.e some examples wouldbe nice or if anyone can recommend a good tutorial on UNIONS in linq.

select top 10 Barcode, sum(ItemDiscountUnion.AmountTaken) from
(SELECT d.Barcode,SUM(AmountTaken) AmountTaken
  FROM [Aggregation].[dbo].[DiscountPromotion] d

  GROUP BY d.Barcode

  UNION ALL

  SELECT i.Barcode,SUM(AmountTaken) AmountTaken
  FROM [Aggregation].[dbo].ItemSaleTransaction i

  group by i.Barcode)  ItemDiscountUnion

  group by Barcode

---

请注意，原始SQL正在合并，这2个选择不将它们连接在一起. 我需要知道如何合并结果，即删除重复项并根据条形码对存在重复项的行金额求和.

---

Note the original SQL is merging the 2 selects NOT concatenating them. I need to know how to merge the results i.e. removing duplicates and summing the rows amount value where there is duplication based on bar code.

推荐答案

对集合进行操作的三个有用的Linq概念.给定集合c和集合e:

Three useful Linq concepts operating on sets. Given set c and set e:

Concat为您提供c或e中的所有内容:

Concat gives you everything in c or e:

(From c In db.Customers Select c.Phone).Concat( _
             From c In db.Customers Select c.Fax).Concat( _
             From e In db.Employees Select e.HomePhone)

(From c In db.Customers _
            Select Name = c.CompanyName, Phone = c.Phone).Concat(From e In db.Employees _
            Select Name = e.FirstName & " " & e.LastName, Phone = e.HomePhone)

联盟还为您提供c和e中的所有内容，但会删除所有重复项:

Union also gives you everything in c and e, but removes any duplicates:

(From c In db.Customers _
        Select c.Country).Union(From e In db.Employees _
        Select e.Country)

除了在c中为您提供的所有内容以外，在e中没有其他内容:

Except gives you everything in c that is not in e:

(From c In db.Customers _
             Select c.Country).Except(From e In db.Employees Select e.Country)

这篇关于如何将sql union转换为linq的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！