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ACC2000: Showing All Records (Including Null) in a Parameter Query

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Summary

When you run a query that takes its parameters from a form, no records are returned by the query if you leave the field blank. If you type an asterisk (*) in the field, only records with non-null values are returned.

This article describes a method that you can use to return all records, including those with null values, when you leave the parameter blank.

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:
207626 ACC2000: Access 2000 Sample Queries Available in Download Center

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More information

The following example is based on the sample database Northwind.mdb.
  1. Create the following macro:
       Macro Name           Action
   ------------------------------
   Run Employee Query   OpenQuery

   Run Employee Query Actions
   ------------------------------
   OpenQuery:
      Query Name: Employee Query
      View: Datasheet
      Data Mode: Edit
  2. Create the following form not based on any table or query:
       Form: Pick Employees
   -------------------------------
   Control: Textbox
      ControlName: Region
   Control: Command Button
      Caption: Run Query
      OnClick: Run Employee Query
  3. Create the following query based on the Employees table:
       Query: Employee Query
   ------------------------------------------------------
   Field: First Name
      Show: True
   Field: Last Name
      Show: True
   Field: Region
      Show: True
      Criteria: Like Forms![Pick Employees]!Region & "*"
      Or: Forms![Pick Employees]!Region Is Null
  4. Open the query in Design view. On the Query menu, click Parameters. Type Forms![Pick Employees]!Region as the Parameter name, with value as the Data Type.
  5. Open the Pick Employees form, type WA in the Region field, and click the Run Query button. Note that the result set contains five employee names.
  6. Open the Pick Employees form, clear the Region field, and click the Run Query button again. Note that the result set now contains nine employee names, four with blank region codes.
By adding the parameter as a field, you can test the parameter and control the other criteria. The equivalent SQL Where condition is as follows: 
   Where Region Like Forms![Pick Employees]!Region & "*"
   Or Forms![Pick Employees]!Region Is Null

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References

For more information about this topic, click Microsoft Access Help on the Help menu, type like operator in the Office Assistant or the Answer Wizard, and then click Search to view the topic.

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Keywords: KB209261, kbhowto

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Article Info
Article ID : 209261
Revision : 2
Created on : 7/15/2004
Published on : 7/15/2004
Exists online : False
Views : 285