Question

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，该程序将所有已删除的客户端写回服务器，然后再将其查询以填充包含结果的专业表。

以下是当前查询：

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

我想做的不是将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的信息填充数据库保存。

我的主要问题是：

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？

或

如何在Microsoft Reports中为Tablix中的项目执行group by子句，以将=Fields!Reason.Value =Fields!Number.Value =Fields!percentage.Value转换为与上述查询返回的结果类似的内容？

Answer 1

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 });

Answer 2

我可以通过两种方式来查询数据表。以下是使用两种方式的示例。

using System;
using System.Data;

namespace WindowsFormsApplication1
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            var deletedClients = GetDataTable();

            // Using linq to create the new DataTable.
            var example1 = deletedClients.AsEnumerable()
                                         .Where(x => x.Field<int>("ClinicId") == 1)
                                         .CopyToDataTable();

            // Using the DefaultView RowFilter to create a new DataTable.
            deletedClients.DefaultView.RowFilter = "ClinicId = 1";
            var rowFilterExample = deletedClients.DefaultView.ToTable();
        }

        static DataTable GetDataTable()
        {
            var dataTable = new DataTable();
            // Assumes ClinicId is an int...
            dataTable.Columns.Add("ClinicId", typeof(int));
            dataTable.Columns.Add("Reason");
            dataTable.Columns.Add("Number", typeof(int));
            dataTable.Columns.Add("Percentage", typeof(float));

            for (int counter = 0; counter < 10; counter++)
            {
                dataTable.Rows.Add(counter, "Reason" + counter, counter, counter);
            }

            return dataTable;
        }
    }
}

如何查询内存中的DataTable以填充另一个数据表

2 个答案: