如何過濾將顯示到datagridview中的數據庫？

Question

我有3個級別的訪問權限，學生，管理員和INSTRUCTOR在一個表中。所以我只想顯示那些是「INSTRUCTOR」的人。感謝我只是一個新手在編碼。

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

用這個替換您的查詢部分;

 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有首選方法，讓數據庫做最擅長的，有你想要的所有數據時代什麼，你需要在本地將其過濾（沒有其它調用數據庫）。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，如果你使用的是「BindingSource」，你也可以過濾它。