SQL 按日期显示每个任务的最新记录

Question

我想为每个任务显示最近更新的记录。目前，无论执行什么任务，我都只会获取所有记录中的最新记录。

这是前端代码

<asp:SqlDataSource ID="GrabAssignedTasks" runat="server" ConnectionString="<%$ ConnectionStrings:DefaultConnection %>" 
            SelectCommand="SELECT Backlog.Story, Tasks.Task, Tasks.EstimatedHours, Tasks.UserStoryTaskID, Tasks_Log.TaskLogID, Tasks_Log.HoursLeft, Tasks_Log.ModifiedDate 
             FROM Backlog 
             INNER JOIN Tasks ON Backlog.UserStoryID = Tasks.UserStoryID 
             INNER JOIN Tasks_Log ON Tasks.UserStoryTaskID = Tasks_Log.TaskID 
             WHERE (Tasks.OwnershipID = @UserID) AND (Tasks_Log.ModifiedDate = (SELECT MAX(ModifiedDate) AS Expr1 
            FROM Tasks_Log AS Tasks_Log_1))">
            <SelectParameters>
                <asp:SessionParameter Name="UserID" SessionField="loggedInUser" />
            </SelectParameters>
        </asp:SqlDataSource>



    </div>
       <header class="jumbotron hero-spacer">

         <asp:Button ID="BackToTasks" runat="server" Text="Back" OnClick="BackToTasks_Click" CssClass="btn btn-primary btn-large" />


        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="GrabAssignedTasks" Height="179px" Width="829px" OnSelectedIndexChanged="HoursChange_SelectedIndexChanged">
            <Columns>
                <asp:BoundField DataField="Story" HeaderText="Story" SortExpression="Story" />
                <asp:BoundField DataField="Task" HeaderText="Task" SortExpression="Task" />
                <asp:BoundField DataField="EstimatedHours" HeaderText="Estimated Hours" SortExpression="EstimatedHours" />
                <asp:BoundField DataField="UserStoryTaskID" HeaderText="UserStoryTaskID" SortExpression="UserStoryTaskID" InsertVisible="False" ReadOnly="True" HeaderStyle-CssClass="hidden-field" ItemStyle-CssClass="hidden-field"/>
                <asp:BoundField DataField="TaskLogID" HeaderText="TaskLogID" SortExpression="TaskLogID" InsertVisible="False" ReadOnly="True" HeaderStyle-CssClass="hidden-field" ItemStyle-CssClass="hidden-field"/>
                <asp:BoundField DataField="HoursLeft" HeaderText="Hours Left" SortExpression="HoursLeft" />
                <asp:BoundField DataField="ModifiedDate" HeaderText="Last Updated" SortExpression="ModifiedDate" />
                <asp:CommandField ShowSelectButton="True" />
            </Columns>
        </asp:GridView>
        </header>

我在 C# 代码中对此没有任何具体说明。

这是我正在使用的数据库中 table 的图片。 Database table

Answer 1

您没有加入 Table Tasks_Log 和 Tasks_Log_1，所以会发生的是 Tasks_Log 中只有修改日期匹配“30/11/ 2015" 得到返回，不管任务。在 Tasks_Log_1 的 WHERE 子句中添加一个条目，以确保您也在正确的 TaskID 上进行匹配：

SELECT Backlog.Story, Tasks.Task, Tasks.EstimatedHours, Tasks.UserStoryTaskID, Tasks_Log.TaskLogID, Tasks_Log.HoursLeft, Tasks_Log.ModifiedDate 
    FROM Backlog 
    INNER JOIN Tasks ON Backlog.UserStoryID = Tasks.UserStoryID 
    INNER JOIN Tasks_Log ON Tasks.UserStoryTaskID = Tasks_Log.TaskID 
    WHERE (Tasks.OwnershipID = @UserID)
    AND (Tasks_Log.ModifiedDate = 
        (SELECT MAX(ModifiedDate) 
         FROM Tasks_Log AS Tasks_Log_1
         WHERE Tasks_Log_1.TaskID = Tasks_Log.TaskID))

SQL 按日期显示每个任务的最新记录

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