Parameter Object (DAO)

  • Article

A Parameter object represents a value supplied to a query. The parameter is associated with a QueryDef object created from a parameter query.

Remarks

Parameter objects allow you to change the arguments in a frequently run QueryDef object without having to recompile the query.

Using the properties of a Parameter object, you can set a query parameter that can be changed before the query is run. You can:

  • Use the Name property to return the name of a parameter.

  • Use the Value property to set or return the parameter values to be used in the query.

  • Use the Type property to return the data type of the Parameter object.

  • Use the Direction property to set or return whether the parameter is an input parameter, an output parameter, or both.

Example

This example demonstrates Parameter objects and the Parameters collection by creating a temporary QueryDef and retrieving data based on changes made to the QueryDef object's Parameters. The ParametersChange procedure is required for this procedure to run.

Sub ParameterX() 
 
 Dim dbsNorthwind As Database 
 Dim qdfReport As QueryDef 
 Dim prmBegin As Parameter 
 Dim prmEnd As Parameter 
 
 Set dbsNorthwind = OpenDatabase("Northwind.mdb") 
 
 ' Create temporary QueryDef object with two 
 ' parameters. 
 Set qdfReport = dbsNorthwind.CreateQueryDef("", _ 
 "PARAMETERS dteBegin DateTime, dteEnd DateTime; " & _ 
 "SELECT EmployeeID, COUNT(OrderID) AS NumOrders " & _ 
 "FROM Orders WHERE ShippedDate BETWEEN " & _ 
 "[dteBegin] AND [dteEnd] GROUP BY EmployeeID " & _ 
 "ORDER BY EmployeeID") 
 Set prmBegin = qdfReport.Parameters!dteBegin 
 Set prmEnd = qdfReport.Parameters!dteEnd 
 
 ' Print report using specified parameter values. 
 ParametersChange qdfReport, prmBegin, #1/1/95#, _ 
 prmEnd, #6/30/95# 
 ParametersChange qdfReport, prmBegin, #7/1/95#, _ 
 prmEnd, #12/31/95# 
 
 dbsNorthwind.Close 
 
End Sub 
 
Sub ParametersChange(qdfTemp As QueryDef, _ 
 prmFirst As Parameter, dteFirst As Date, _ 
 prmLast As Parameter, dteLast As Date) 
 ' Report function for ParameterX. 
 
 Dim rstTemp As Recordset 
 Dim fldLoop As Field 
 
 ' Set parameter values and open recordset from 
 ' temporary QueryDef object. 
 prmFirst = dteFirst 
 prmLast = dteLast 
 Set rstTemp = _ 
 qdfTemp.OpenRecordset(dbOpenForwardOnly) 
 Debug.Print "Period " & dteFirst & " to " & dteLast 
 
 ' Enumerate recordset. 
 Do While Not rstTemp.EOF 
 
 ' Enumerate Fields collection of recordset. 
 For Each fldLoop In rstTemp.Fields 
 Debug.Print " - " & fldLoop.Name & " = " & fldLoop; 
 Next fldLoop 
 
 Debug.Print 
 rstTemp.MoveNext 
 Loop 
 
 rstTemp.Close 
 
End Sub