如何過濾顯示在datagridview中的數據庫？

Question

我有3級訪問權限，表中有STUDENT，ADMIN和INSTRUCTOR。 所以我想只展示那些“講師”。 謝謝我只是編碼的新手。

 Me.cboSearchBy.SelectedIndex = 0
        Dim conn As New OleDbConnection
        Dim cmd As New OleDbCommand
        Dim da As New OleDbDataAdapter
        Dim dt As New DataTable
        Dim sSQL As String = String.Empty

        Try

            conn = New OleDbConnection(Get_Constring)
            conn.Open()
            cmd.Connection = conn
            cmd.CommandType = CommandType.Text
            sSQL = "SELECT Username, lname + ', ' + fname + ' ' + mname as name, password FROM Instructor"
            If Me.cboSearchBy.Text = "Name" Then
                sSQL = sSQL & " where lname + ', ' + fname + ' ' + mname like '%" & Me.txtSearch.Text & "%'"
            Else
                sSQL = sSQL & " where Username =" & Me.txtSearch.Text
            End If
            cmd.CommandText = sSQL
            da.SelectCommand = cmd
            da.Fill(dt)

            Me.dtgResult.DataSource = dt
            If dt.Rows.Count = 0 Then
                MsgBox("No record found!")
            End If

        Catch ex As Exception
            MsgBox(ErrorToString)
        Finally
            conn.Close()
        End Try

Answer 1

用此替換您的查詢部分;

     sSQL = "SELECT Username, lname + ', ' + fname + ' ' + mname as name, password FROM Instructor"
     If Me.cboSearchBy.Text = "Name" Then
        sSQL = sSQL & " where lname + ', ' + fname + ' ' + mname like '%" & Me.txtSearch.Text & "%'"
        sSQL = sSQL & " and  level like '%instructor%'"
     Else
        sSQL = sSQL & " where Username =" & Me.txtSearch.Text
        sSQL = sSQL & " and  level like '%instructor%'"
     End If

Answer 2

雖然@Nadeem_MK具有首選方法，但讓數據庫執行最佳操作，有時您需要所有數據，並且需要在本地過濾它（無需再次調用數據庫）。 你可以這樣做的一種方法是：

...Your code
da.SelectCommand = cmd
da.Fill(dt)
'Filter locally
dim drs as datarow() = dt.select("level = 'Instructor'")
'Use the datarow array as your datasource instead of the data table
Me.dtgResult.DataSource = drs

或者，如果您使用的是“BindingSource”，也可以對其進行過濾。