条件を満たすレコードの合計

        SqlDataAdapter adapter = new SqlDataAdapter("select 取引日,取引先,売価 
                from 取引履歴テーブル ", connectionString);
        SqlDataAdapter adapter2 = new SqlDataAdapter("select distinct 取引日 
                from 取引履歴テーブル ", connectionString);
        DataSet ds = new DataSet("ds1");
        adapter.Fill(ds, "table1");
        adapter2.Fill(ds,"distinct");

        ds.Tables["distinct"].ChildRelations.Add(ds.Tables["distinct"].Columns["取引日"],
                 ds.Tables["table1"].Columns["取引日"]);

        foreach (DataRow row in ds.Tables["table1"].Rows)
        {
            string name = (string)row["取引先"];
            //既知の取引先でない場合カラムを追加
            if (!ds.Tables["table1"].Columns.Contains(name))
            {
                DataColumn colsum = new DataColumn(name, typeof(int));
                colsum.Expression = "IIF( 取引先='" + name + "' , 売価 , 0 )";
                ds.Tables["table1"].Columns.Add(colsum);

                DataColumn col1 = new DataColumn(name);
                col1.Expression = "Sum(Child." + name + ")";
                ds.Tables["distinct"].Columns.Add(col1);
            }
        }