使用 C# 查询未在 MS Access 中返回结果? [英] Query is not returning results in MS Access with C#?

问题描述

所以我有一个相对简单的查询，但它不匹配 full_name 文本字段，即使我可以看到数据在那里并且完全匹配?

So I have a relatively simple query, but it is not matching the full_name text field even though I can see the data is there and is an exact match?

我确保检查传入的 fullName 参数是否正确.我找不到任何文档来验证我是否需要单引号，但如果没有它，则会引发错误.

I made sure to checkk the fullName parameter being passed in is the correct value. I couldn't find any documentation verifying if I needed the single quotes or not, but without it an error was thrown.

大家有什么建议吗?

与 SQL 语句相关的代码?

Code in question with the SQL statement?

    public static ObservableCollection<ShiftView> GetShifts(DateTime? start, DateTime? stop, string fullName, bool? closed)
    {
        ObservableCollection<ShiftView> shifts = new ObservableCollection<ShiftView>();

        // INFO: Not intended to retrieve a lot of records as there is no caching....
        OleDbCommand cmd = new OleDbCommand("SELECT profiles.profile_id, profiles.full_name, shifts.start, shifts.stop, shifts.start_log, shifts.stop_log, shifts.start_notes, shifts.stop_notes FROM shifts, profiles WHERE " + 
            (start.HasValue ? "(shifts.start>=@start) AND " : "") +  
            (stop.HasValue ? "(shifts.stop<=@stop) AND " : "") +
            (fullName != null ? "profile.full_name='@full_name' AND " : "") +
            (closed.HasValue ? "shifts.closed=@closed AND " : "") +
            "(shifts.profile_id=profiles.profile_id)"
            );

        if (start.HasValue)
            cmd.Parameters.AddWithValue("@start", start.Value.ToString());
        if (stop.HasValue)
            cmd.Parameters.AddWithValue("@stop", stop.Value.ToString());
        if (fullName != null)
            cmd.Parameters.AddWithValue("@full_name", fullName);
        if (closed.HasValue)
            cmd.Parameters.AddWithValue("@closed", closed);
        OleDbDataReader reader = Database.Read(cmd);

        DateTime? _stop, _stopLog;

        while(reader.Read())
        {
            Console.WriteLine("!");
            // shorthand form if's with ? does not work here.
            if (reader.IsDBNull(reader.GetOrdinal("stop")))
                _stop = null;
            else
                _stop = reader.GetDateTime(reader.GetOrdinal("stop"));

            if (reader.IsDBNull(reader.GetOrdinal("stop_log")))
                _stopLog = null;
            else
                _stopLog = reader.GetDateTime(reader.GetOrdinal("stop_log"));

            shifts.Add(new ShiftView(
                reader.GetString(reader.GetOrdinal("profile_id")), 
                reader.GetString(reader.GetOrdinal("full_name")),
                reader.GetDateTime(reader.GetOrdinal("start")),
                _stop,
                reader.GetDateTime(reader.GetOrdinal("start_log")),
                _stopLog,
                reader.GetString(reader.GetOrdinal("start_notes")),
                reader.GetString(reader.GetOrdinal("stop_notes"))
                ));
        }

        return shifts;
    }

从这个按钮按下时调用上面的代码:

The above code gets called from this button press:

    private void ShowStatsButton_Click(object sender, RoutedEventArgs e)
    {
        DateTime? start = StartDatePicker.SelectedDate;
        DateTime? stop = StopDatePicker.SelectedDate;
        string name = NameComboBox.Text;

        if (name.Equals("Everyone"))
            name = null;

        if (stop.HasValue)
            stop = stop.Value.AddDays(1);

        StatsGridView.ItemsSource = Shift.GetShifts(start, stop, name, true);
    }

这会过滤日期范围以及是否有全名.我确保 name 有一个有效的值.

This filters the date range and if there is a full name. I ensure there is a valid value for name.

推荐答案

事实证明，在表名中添加是导致问题的原因.为什么会这样，尚不确定，我将跟进另一个具体的问题.

It turns out that adding in the table name was the cause of the problem. Why this is the case, is uncertain and I will follow up with another question specific to that.

所以我最终采用的解决方案更改了以下内容:

So the solution I eventually went with to change the following:

    OleDbCommand cmd = new OleDbCommand("SELECT profiles.profile_id, profiles.full_name, shifts.start, shifts.stop, shifts.start_log, shifts.stop_log, shifts.start_notes, shifts.stop_notes FROM shifts, profiles WHERE " + 
        (start.HasValue ? "(shifts.start>=@start) AND " : "") +  
        (stop.HasValue ? "(shifts.stop<=@stop) AND " : "") +
        (fullName != null ? "profile.full_name='@full_name' AND " : "") + // this is where the problem is
        (closed.HasValue ? "shifts.closed=@closed AND " : "") +
        "(shifts.profile_id=profiles.profile_id)"
        );

并将其更改为:

        (fullName != null ? "full_name=@full_name AND " : "") + // Notice I removed the table name and just straight referenced the field.

我更新了上面正确的行以删除单引号，这是我在复制和粘贴时不小心留下的(numero uno 编码错误！).

I updated the above correct line to remove single quotes, that I accidentally left in copy and pasting (numero uno coding mistake!).

我还发现了为什么我盯着它看几个小时总是出错.原来，该表被称为配置文件"，而不是配置文件"，因此当我删除表名时，它起作用了！

I also discovered why I kept getting an error staring at it for hours. Turns out, the table is called "profiles", not "profile" and therefore when I removed the table name it worked!

所以另一种解决方案是:

So an alternative solution is:

(fullName != null ? "profiles.full_name=@full_name AND " : "") 

傻，我知道.现在觉得自己很傻.

Silly, I know. Feel stupid now.

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