[英]LINQ to SQL - Distinct records across multiple columns
我有一個關於我用LINQ編寫的查詢的查詢,希望有人可以提供幫助。 基本上我有以下內容(示例數據)
ProductCode LanguageID LegislationId Version
1234 English UK 1
1234 English UK 2
5678 English UK 1
9999 English UK 1
9999 English UK 2
9999 Spanish Spain 1
因此,我需要做的是根據用戶提供的條件(包括LanguageID和Description)返回記錄。 這里最棘手的部分是,在相同產品代碼,語言和法規存在多個版本的情況下,我只想返回最新版本。
所以...我的代碼如下(pLegislations包含以逗號分隔的立法列表):
List<string> legList = pLegislations.Split(',').ToList();
IEnumerable<MyClass> results = null;
results = (from a in context.ALLProducts
let prodCode = a.ProductCode
let prodDesc = a.ProductDescription
where legList.Contains(a.LegislationID) &&
(a.LanguageID == pLanguage || pLanguage == null) &&
a.BrandName == pMarket &&
(prodCode.Contains(pSearch) || prodDesc.Contains(pSearch) ||
pSearch == string.Empty) &&
prodCode[0] != 'x' &&
((pMarket == "testMarket") ? prodCode.StartsWith("0") : true)
select new MyClass
{
BrandName = a.BrandName,
BulkCode = prodCode,
BulkDescription = prodDesc,
Language = a.LanguageName,
LanguageCode = a.LanguageID
}).ToList();
現在,在沒有多個版本的情況下,這一切都可以正常工作,所以我的問題是-當ProductCode,Language和Legislation匹配時,即如果我要傳遞Language =',我應該如何過濾它,以便僅返回最新版本。英語”和法律=“英國”,那么我期望得到以下結果:
ProductCode LanguageID LegislationId Version
1234 English UK 2
5678 English UK 1
9999 English UK 2
9999 Spanish Spain 1
提前致謝
安德魯
將結果按ProductCode
(1)分組,然后從每個分組項目中選擇具有最大Version
值(2)的項:
results = (from a in context.ALLProducts
let prodCode = a.ProductCode
let prodDesc = a.ProductDescription
where legList.Contains(a.LegislationID) &&
(a.LanguageID == pLanguage || pLanguage == null) &&
a.BrandName == pMarket &&
(prodCode.Contains(pSearch) ||
prodDesc.Contains(pSearch) ||
pSearch == string.Empty) &&
prodCode[0] != 'x' &&
((pMarket == "testMarket") ? prodCode.StartsWith("0") : true)
group a by a.ProductCode into g // 1
let lastProduct = g.OrderByDescending(x => x.Version).First() // 2
select new MyClass
{
BrandName = lastProduct.BrandName,
BulkCode = prodCode,
BulkDescription = prodDesc,
Language = lastProduct.LanguageName,
LanguageCode = lastProduct.LanguageID
}).ToList();
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