Question

此代码返回零行数，但appointment表中有2行。

我评论过的msgbox是检查日期是否正确，格式是否正确，并将日期显示为2014/08/09。数据库中的预约日期为2014/08/09，共有2条记录（仅有2条记录）。记录计数变量显示为0。

表名（直接复制并粘贴）为Appointments，列为AppointmentDate。

connectDatabase子例程连接到数据库成功，因为每当我连接到数据库时它都会使用它，所以它正确，因为我在使用相同的子例程运行此代码之前正确连接到其他表。

Command.text包含

SELECT * FROM Appointments WHERE AppointmentDate = 2014/08/09

不知道要指定的其他细节。

Private Sub frmAppointments_Load(sender As Object, e As EventArgs) Handles MyBase.Load             
          'load appointments
           LoadAppointments(dtpAppointmentDate.Value.Date) 
    End Sub

    Public Sub LoadAppointments(whichdate As Date)
           Dim sqlcmd As New OleDb.OleDbCommand

           'set connection
           ConnectDatabase()

           With frmAppointments
               'MsgBox(whichdate)                   
                M_connDB.Open()
               'fetch records from database
               sqlcmd.Connection = M_connDB
               sqlcmd.CommandText = "SELECT * FROM Appointments WHERE AppointmentDate = " & whichdate
               .dataAdapterAppointments = New OleDb.OleDbDataAdapter(sqlcmd.CommandText, M_connDB)
               'first clear data table to prevent duplicates
               .dataTableAppointments.Rows.Clear()
               .dataAdapterAppointments.Fill(.dataTableAppointments)
               M_connDB.Close()

               Dim rowindex As String
               Dim iy As Long
               Dim recordcount As Long

               'check if any records exist
               recordcount = .dataTableAppointments.Rows.Count
               If Not recordcount = 0 Then
                    For iy = 0 To .dataTableAppointments.Rows.Count
                          For Each row As DataGridViewRow In .dtgrdAppointments.Rows
                              If row.Cells(0).Value = .dataTableAppointments.Rows(iy).Item(6) Then
                                  rowindex = row.Index.ToString()
                                  MsgBox(.dtgrdAppointments.Rows(rowindex).Cells(0).Value, vbInformation + vbOKOnly, "MSG")
                                 Exit For
                            End If
                          Next
                    Next iy
               Else
                    MsgBox("No Appointments for selected date.", vbInformation + vbOKOnly, "No Appoinments")
               End If
           End With

Answer 1

使用sql-parameters而不是string-concatenation。这应该在MS Access中起作用：

sqlcmd.CommandText = "SELECT * FROM Appointments WHERE AppointmentDate = ?"
sqlcmd.Parameters.AddWithValue("AppointmentDate", whichdate)

这可以防止转换或本地化问题，甚至更重要的是-sql-injection。

Answer 2

2014/08/09没有引号，使其成为数学表达式（2014除以8除以9）。当然，您的表没有行，其日期与该表达式的结果相匹配。但是不要加上引号。而是添加一个参数。

Answer 3

我不是VB，所以我用C＃编写。我的观点是，指定数据类型也是更好的选择：

sqlcmd.CommandText = "SELECT * FROM Appointments WHERE AppointmentDate=@whichdate";
sqlcmd.Parameters.Add("@whichdate", SqlDbType.Date).Value = whichdate;

SQL QUERY返回0记录但存在2条记录

3 个答案: