如何查询/将数据转换为所需的格式

Posted 2023-04-12

【中文标题】如何查询/将数据转换为所需的格式

【英文标题】：How to query / transform the data into the desired format

【发布时间】：2021-12-05 09:26:50

【问题描述】：

我想知道是否有人可以帮助我将以下数据（来自数据库）转换为 列表：

Lorryid	productid	qtytype	Qty	iscomment	comment
1	4090	3	2	f
1	4153	3	1	f
1	4153	3	1	f
1	4153	3	1	f
1	4153	3	1	f
1	4153	3	1	f
1	31068	3	2	f
1	31069	3	2	f
1	31173	3	2	f
2	17	0	1.000	f
2	150	3	6.000	f
2	216	3	6.000	f
2	278	2	1.020	f
2	398	2	1.125	f
2	398	2	1.090	f
2	398	2	0	t	MUST BE RIPE
2	431	2	3.000	f
2	436	3	1.000	f
2	446	0	1	f
2	446	2	3.045	f
2	451	3	2.000	f
2	457	3	1.000	f
2	458	3	4.000	f
2	478	3	1.000	f
2	510	2	1.140	f
2	518	3	3.000	f
2	518	3	4.000	f
2	550	2	1.170	f
2	550	3	1.000	f

进入下面的对象。

public class View

  public List<LorryLoading> Report


public class LorryLoading

  public int LorryId
  public List<Product> Product


public class Product

  public int ProductId
  public decimal Qty0 sum(Quantity) WHERE QtyType = 0
  public decimal Qty2 sum(Quantity) WHERE QtyType = 2
  public decimal Qty3 sum(Quantity) WHERE QtyType = 3
  public List<string> Comments

是否可以使用单个投影？分配列表时遇到问题。

另外，我可以学习这种转换的任何链接？例子 到目前为止，我发现它们相当简单或解释不清。

【参考方案1】：

您可以使用 Linq 的 Aggregate 进行自定义聚合。这稍微复杂一些，因为您在这里进行了双重聚合。

请注意，这可能仅适用于 Linq-to-Objects。

var report = data
    .GroupBy(row => row.Lorryid)
    .Select(l => new LorryLoading 
        LorryId = l.Key,
        Product = l
            .GroupBy(row => row.productid)
            .Select(p => p.Aggregate(
                new Product ProductId = p.Key,  // this is the starting object
                (prod, row) =>                   // this aggregates it up
                    if(comment != null)
                        prod.Comments.Add(row.comment);
                    if(QtyType == 0)
                        prod.Qty0 += row.Quantity;
                    else if(QtyType == 2)
                        prod.Qty2 += row.Quantity;
                    else if(QtyType == 3)
                        prod.Qty3 += row.Quantity;
                )
            .ToList()
     ).ToList();

var view = new View Report = report;

【参考方案2】：

您要问的是转换，因此没有简单的投影。你可以用一个超级复杂的语句来做到这一点，这会让你的同事在必须维护时换工作:) 我的建议是不要试图给校园留下深刻印象，而是专注于干净的代码：

var lorryLoadingReport = new List<ReportData>();
//Presume you already have data into a transport object and know how to read that, as it wasn't your question

var view = new View

    Report = new List<LorryLoading>()
;
var listOf = new List<Product>();
        
//Lets not over complicate our mind, just keep it simple, let's get the products and the lorries
var productsList = lorryLoadingReport.Select(x => x.ProductId).ToList();
var lorriesList = lorryLoadingReport.Select(x => x.LorryId).ToList();
foreach (var lorry in lorriesList)

    //We'll need an entry even if the list will be empty
    var lorryLoading = new LorryLoading
    
        LorryId = lorry,
        Product = new List<Product>()
    ;

    //Get the respective subset
    var lorryLoadingReportPerLorry = lorryLoadingReport.Where(l => l.LorryId == lorry);
    if (lorryLoadingReportPerLorry.Any())
    
        foreach (var productId in productsList)
        
            //And add a product with all 4 sums iteratively
            var p = new Product
            
                ProductId = productId,
                Comments = new List<string>()
            ;
            var commentsList = lorryLoadingReport.Where(x => x.ProductId == productId && x.IsComment == "t").Select(s => s.Comment).ToList();
            if(commentsList.Any())
                p.Comments.AddRange(commentsList);
            p.Qty0 = lorryLoadingReport.Where(x => x.Qty == 0).Sum(y => y.Qty);
            p.Qty2 = lorryLoadingReport.Where(x => x.Qty == 2).Sum(y => y.Qty);
            p.Qty3 = lorryLoadingReport.Where(x => x.Qty == 3).Sum(y => y.Qty);

            lorryLoading.Product.Add(p);
        
        
    view.Report.Add(lorryLoading);

【讨论】：

显然示例可以在代码审查之前清理很多，并且应该，但是为了清楚地向某人概述一个解决方案，没有给出更接近的示例，我认为它可以说明解决问题的简化方法，它确实有助于转换

谢谢。正在做类似的事情来实现结果，但通过从数据库中选择来完成分组。我同意可维护的>花哨的代码。