每次显示或加载表单时，用当前日期填充一列

Question

我想用当前日期填充一列中的所有条目，这样我就可以将其与测试日期列进行比较，并确定自上次测试以来的天数。我想我能算出天数，但我不知道如何用当前日期填充这一栏。

Private Sub Reports_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown
mySql = "Update Studentdata, SET currentDate = Date()"
ConnDB()
myCommand = New OleDbCommand(mySql, myConnection)
End Sub

Answer 1

您真的在执行update命令吗？试试这个：

Dim myConnection As New OleDb.OleDbConnection()  'Complete as needed
Dim mySql As String = "Update Studentdata SET currentDate = Date()"
Using cmd As New OleDb.OleDbCommand(mySql, myConnection)
Try
cmd.Connection.Open()
cmd.ExecuteNonQuery()
Catch ex As Exception
MessageBox.Show(ex.Message, "ERROR UPDATING")
Finally
cmd.Connection.Close()
End Try
End Using

或者尝试从代码中填充Date并将其作为参数提供，如下所示：

Using cmd As New OleDb.OleDbCommand()
cmd.Connection = myConnection
Try
cmd.Connection.Open()
cmd.CommandText = "Update Studentdata SET currentDate = @Date"
cmd.Parameters.Add(New OleDb.OleDbParameter("@Date", DateTime.Now))
cmd.ExecuteNonQuery()
Catch ex1 As Exception
MessageBox.Show(ex1.Message, "ERROR UPDATING")
Finally
cmd.Connection.Close()
End Try
End Using

Answer 2

据我所知，访问数据库的日期可能会有一些问题，包括毫秒，所以你可以这样做(并删除"SET"之前的逗号(：

Dim dateWithoutMiliseconds as DateTime = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day)
mySql = String.Format("Update Studentdata SET currentDate = {0}", dateWithoutMiliseconds)