ACC2000: How to Create a Parameter In() Statement

This article demonstrates two methods that you can use to pass multiple values to a query by using a parameter prompt. The first method uses the Instr() function to parse the parameter values entered when the query is run. The second method describes a way to create a query by using the In() operator with multiple values.

NOTE: You can see a demonstration of the technique that is used in this article in the sample file Qrysmp00.exe. For information about how to obtain this sample file, please see the following article in the Microsoft Knowledge Base: NOTE: The sample code in this article uses Microsoft Data Access Objects. For this code to run properly, you must reference the Microsoft DAO 3.6 Object Library. To do so, click References on the Tools menu in the Visual Basic Editor, and make sure that the Microsoft DAO 3.6 Object Library check box is selected.

Method 1

The following method demonstrates how to use the Instr() function to pass multiple values, separated by commas, to a parameter query.

CAUTION: If you follow the steps in this example, you modify the sample database Northwind.mdb. You may want to back up the Northwind.mdb file and follow these steps on a copy of the database.

1. Start Microsoft Access, and then open the sample database Northwind.mdb.
2. Create the following new query based on the Employees table:
   Query: ParamQuery
   Type: Select Query
   
   Field: EmployeeID
   Table: Employees
   Show: True
   
   Field: LastName
   Table: Employees
   Show: True
3. In the next empty column on the query grid, type the following expression and attributes:
   Field: InStr([Last Names separated by commas,Blank=All],[LastName])
   Criteria: > 0 Or Is Null
   Show: False
   Save the query as ParamQuery.
4. On the View menu, click Datasheet View, and then type the following last names, separated by commas, into the Enter Parameter Value dialog box:
   Fuller,King,Callahan

NOTE: Three records are returned. If you leave the parameter blank, the query returns all records.

Method 2

The following method uses a query that calls a function and passes it two parameters. The first parameter is the name of a field that exists in the table on which the query is based. The second parameter prompts the user to type a list of values. The function processes the user's entries as the list of multiple parameters for the In() operator.

Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements. CAUTION: If you follow the steps in this example, you modify the sample database Northwind.mdb. You may want to back up the Northwind.mdb file and follow these steps on a copy of the database.

1. Start Microsoft Access, and then open the sample database Northwind.mdb.
2. Create a new module with the following two functions:

   '************************************************************
   'Declarations section of the module.
   '************************************************************
   
   Option Explicit
   
   '============================================================
   ' The GetToken() function defines the delimiter character.
   '============================================================
   
   
   Function GetToken (stLn, stDelim)
      Dim iDelim as Integer, stToken as String
      iDelim = InStr(1, stLn, stDelim)
      If (iDelim <> 0) Then
         stToken = LTrim$(RTrim$(Mid$(stLn, 1, iDelim - 1)))
         stLn = Mid$(stLn, iDelim + 1)
      Else
         stToken = LTrim$(RTrim$(Mid$(stLn, 1)))
         stLn = ""
      End If
      GetToken = stToken
   End Function
   
   '============================================================
   ' The InParam() function is the heart of this article. When
   ' the query runs, this function causes a query parameter
   ' dialog box to appear so you can enter a list of values.
   ' The values you enter are interpreted as if you
   ' had entered them within the parentheses of the In() operator.
   '============================================================
   Function InParam (Fld, Param)
      Dim stToken as String
      'The following two lines are optional, making queries
      'case-insensitive
      Fld = UCase(Fld)
      Param = UCase(Param)
      If IsNull(Fld) Then Fld = ""
      Do While (Len(Param) > 0)
         stToken = GetToken(Param, ",")
         If stToken = LTrim$(RTrim$(Fld)) Then
            InParam = -1
            Exit Function
         Else
            InParam = 0
         End If
      Loop
   End Function
   					

3. Close and save the module.
4. Create a new query based on the Customers table. Drag any fields that you want to the query grid.
5. Add the following field to the query grid:
   NOTE: In the following example, an underscore (_) at the end of a line is used as a line-continuation character. Remove the underscore from the end of the line when re-creating this example.
   Field Name: InParam([CustomerID],[ Enter ID list using _
   commas and no spaces:])
   Show: False
   Criteria: True
   NOTE: The value InParam(...) shown for the Field Name should be typed as one statement on a single line. The InParam() function works with Integer fields as well as with Text fields.
6. Run the query. Note that you are prompted to type a list of parameters. The following message is displayed in the dialog box:
   Enter ID list using commas and no spaces:
7. In the Enter Parameter Value box, type:
   CHOPS,EASTC,FAMIA
   Notice that all records that meet the criteria are displayed. If you type no parameters, no records are returned.

NOTE: One limitation of the In() operator is that it does not support wildcards, such as * or ?. For example, Microsoft Access cannot run the following query:

For more information about the In operator, in the Visual Basic Editor, click Microsoft Visual Basic Help on the Help menu, type in operator example (dao) in the Office Assistant or the Answer Wizard, and then click Search to view the topic.