将参数传递给命名命令

正如命令的结果作为命名命令的 变量传出时,参数化命令的参数可以作为 传入到命名命令 变量中。

下面的代码示例尝试从 Northwind 数据库中检索其 CustomerID 为“ALKFI”的客户下达的所有订单。 调用命名命令时,会提供 CustomerID 的值。

Const DS = "MySqlServer"  
Const DB = "Northwind"  
Const DP = "SQLOLEDB"  
  
Dim objConn As New ADODB.Connection  
Dim objRs As New ADODB.Recordset  
Dim objComm As New ADODB.Command  
  
CommandText = "SELECT OrderID, OrderDate, " & _  
                     "RequiredDate, ShippedDate " & _  
                     "FROM Orders " & _  
                     "WHERE CustomerID = ? " & _  
                     "ORDER BY OrderID"  
  
ConnectionString = "Provider=" & DP & _  
                   ";Data Source=" & DS & _  
                   ";Initial Catalog=" & DB & _  
                   ";Integrated Security=SSPI;"  
  
' Connect to the data source.  
objConn.Open ConnectionString  
  
' Set a named command.  
objComm.CommandText = CommandText  
objComm.CommandType = adCmdText  
objComm.Name = "GetOrdersOf"  
Set objComm.ActiveConnection = objConn  
  
' Call the named command, passing a CustomerID value  
' as the input parameter.   
'    "ALFKI" is the required input parameter,  
'    objRs is the resultant output variable.  
objConn.GetOrdersOf "ALKFI", objRs  
  
' Display the result.  
Debug.Print "All orders by ALFKI:"  
Do While Not objRs.EOF  
    Debug.Print vbTab & objRs(0) & vbTab & objRs(1) & vbTab & _  
                objRs(2) & vbTab & objRs(3)  
    objRs.MoveNext  
Loop  
  
' Clean up.  
objRs.Close  
objConn.Close  
Set objRs = Nothing  
Set objConn = Nothing  
Set objComm = Nothing  

请注意,所有输入参数必须位于任何输出变量之前,参数的数据类型必须匹配或可转换为相应字段的数据类型。 以下语句 -

objConn.GetOrdersOf 12345, objRs  

- 将导致数据类型不匹配,因为所需的输入参数是字符串 类型的,而不是 整数 类型。

以下调用 -

objConn.GetOrdersOf "12345", objRs  

- 有效,但会生成空结果集,因为数据库中不存在此类记录。

另请参阅

连接对象 (ADO)