如何选择具有分组LINQ查询的联接字段

时间:2016-05-20 14:27:55

标签: c# linq

我已经搜索了网站,并通过几种不同的方式切片和切块,但我是LINQ的新手,我无法弄清楚如何从我的联合表中选择字段。每次我运行这个时我都会收到一条消息:

  

"列UPC不属于表。"

     

"列条目不属于表。"

audits表的每个文件名都有一行数据,scanDetail表有多个与每个文件名相关联的行。我需要加入表格,对数据进行分组,然后选择不同数量的UPC,并且只显示最大条目数,这样每个文件名都有一行数据。

var query = from audit in audits.AsEnumerable()                
            join scan in scanDetail.AsEnumerable()
            on audit.Field<string>("filename") equals scan.Field<string>("filename")
            group audit by audit.Field<string>("filename") into g
            select new
            {
               Account = g.Select(x => x.Field<string>("Account")),
               Store = g.Select(x => x.Field<string>("Store")),
               AuditDate = g.Select(x => x.Field<string>("AuditDate")),
               UPCs = g.Select(x => x.Field<string>("UPC").Distinct().Count()),
               Qty = g.Select(x => x.Field<string>("ScanQty")),
               Retail = g.Select(x => x.Field<string>("RegTotal")),
               Entries = g.Select(x => x.Field<string>("Entry").Max()),
               Supervisor = g.Select(x => x.Field<string>("AuditSup")),
               Division = g.Select(x => x.Field<string>("StoreDivision")),
               Invoice = g.Select(x => x.Field<string>("InvAmount"))
           };

我用这种方式尝试了同样的结果。

  var query = 
           from audit in audits.AsEnumerable()  

           join scan in scanDetail.AsEnumerable()
           on audit.Field<string>("filename") equals
            scan.Field<string>("filename")
           group audit by new {storeDisk = audit.Field<string>("filename"), 
                               Account = audit.Field<string>("Account"),
                               Store = audit.Field<string>("Store"),
                               AuditDate = audit.Field<string>("AuditDate"),
                               UPCs = (from UPC in scanDetail.AsEnumerable()
                                       select scan.Field<string>("UPC")),
                               Qty = audit.Field<string>("ScanQty"),
                               Retail = audit.Field<string>("RegTotal"),
                               Entries = (from Entry in scanDetail.AsEnumerable()
                                         select scan.Field<string>("Entry")),
                               Supervisor = audit.Field<string>("AuditSup"),
                               Division = audit.Field<string>("StoreDivision"),
                               Invoice = audit.Field<string>("InvAmount")
           } into g
           select new
           {

               Account = g.Key.Account,
               Store = g.Key.Store,
               AuditDate = g.Key.AuditDate,
               UPCs = g.Select(x => x.Field<string>("UPC").Distinct().Count()),
               Qty = g.Key.Qty,
               Retail = g.Key.Retail,
               Entries = g.Select(x => x.Field<string>("Entry").Max()),
               Supervisor = g.Key.Supervisor,
               Division = g.Key.Division,
               Invoice = g.Key.Invoice

           };

2 个答案:

答案 0 :(得分:0)

你基本上需要从你需要的audit中取出所有内容并将其放入&#34;键&#34;小组。

var query = from audit in audits.AsEnumerable()                
            join scan in scanDetail.AsEnumerable()
            on audit.filename equals scan.filename
            group audit by new { audit.Account, audit.Store, etc... } into g
            select new
            {
               g.Key.Account,
               g.Key.Store,
               // etc for the rest of the audit fields
               Entries = g.Max(x => x.Entry),
               UPCs = g.Select(x => x.UPC).Distinct().Count()),
           };

答案 1 :(得分:0)

由于&#34;审核表的每个文件名都包含一行数据&#34; ,因此无需对该表中的数据进行分组。在这种情况下,您可以使用group join代替常规联接,而documentation则根据{{3}}:

  

根据键相等性将两个序列的元素相关联,并对结果进行分组。

换句话说,对于外部表的每个元素,您将从内部表中获得 set 相关元素。然后,您可以在该集上执行不同的聚合。请记住,该集合可以为空,并且在这种情况下,某些聚合会抛出异常。

话虽如此,查询可能是这样的:

var query = from audit in audits.AsEnumerable()                
            join scan in scanDetail.AsEnumerable()
            on audit.Field<string>("filename") equals scan.Field<string>("filename")
            into scanGroup
            select new
            {
               Account = audit.Field<string>("Account"),
               Store = audit.Field<string>("Store"),
               AuditDate = audit.Field<string>("AuditDate"),
               UPCs = scanGroup.Select(scan => scan.Field<string>("UPC")).Distinct().Count(),
               Qty = audit.Field<string>("ScanQty"),
               Retail = audit.Field<string>("RegTotal"),
               Entries = scanGroup.Select(scan => scan.Field<string>("Entry")).OrderByDescending(x => x).FirstOrDefault(),
               Supervisor = audit.Field<string>("AuditSup"),
               Division = audit.Field<string>("StoreDivision"),
               Invoice = audit.Field<string>("InvAmount")
           };