c# – 如何查询内存中的DataTable以填充另一个数据表

我正在尝试更新Microsoft报告.它的作用是写出从转换过程中排除的客户数量以及原因.目前,程序将所有已删除的客户端写回服务器,然后将其查询回来以填充带有结果的专业表.

这是当前的查询：

SELECT  DeletedClients.Reason,COUNT(DeletedClients.Reason) AS Number,CAST(CAST(COUNT(DeletedClients.Reason) AS float) 
            / CAST(t.Total AS float) 
            * 100 AS numeric(4,1)) AS percentage
FROM DeletedClients CROSS JOIN
    (SELECT COUNT(*) AS Total
    FROM DeletedClients AS DeletedClients_1
    WHERE (ClinicID = @ClinicID)) AS t
WHERE (DeletedClients.ClinicID = @ClinicID) 
    AND (DeletedClients.TotalsIdent = @ident)
GROUP BY DeletedClients.Reason,t.Total
ORDER BY Number DESC

我想做的是不将DeletedClients写入服务器,因为它已作为DataTable存在于我的程序的内存中,它只会减慢报告速度并使用我们不需要保存的信息填充数据库.

我的主要问题是：要么：

如何查询数据表以创建一个新的内存数据表,其结果与我写出sql服务器并使用上面的查询读回来的结果相同？

要么

如何在Microsoft Reports中为Tablix中的项目执行group by子句= Fields！Reason.Value = Fields！Number.Value = Fields！percentage.Value类似于上面查询的返回结果？

解决方法

您可以使用DataTable.Select查询DataTable.

DataTable table = GetDataTableResults();
DataTable results = table.Select("SomeIntColumn > 0").copyToDataTable();

或者对于更复杂的查询,您可以使用LINQ查询DataTable：

DataTable dt = GetDataTableResults();

var results = from row in dt.AsEnumerable()
              group row by new { SomeIDColumn = row.Field<int>("SomeIDColumn") } into rowgroup
              select new
              {
                  SomeID = rowgroup.Key.someIDColumn,Sometotal = rowgroup.Sum(r => r.Field<decimal>("SomeDecimalColumn"))
              };                    

DataTable queryResults = new DataTable();
foreach (var result in query)
    queryResults.Rows.Add(new object[] { result.someID,result.sometotal });

原文地址：https://www.jb51.cc/csharp/97062.html