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

This article was previously published under Q209261
Moderate: Requires basic macro, coding, and interoperability skills.

This article applies only to a Microsoft Access database (.mdb).

SUMMARY
When you run a query that takes its parameters from a form, norecords are returned by the query if you leave the field blank. If youtype an asterisk (*) in the field, only records with non-null valuesare 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 MicrosoftKnowledge Base:
207626 ACC2000: Access 2000 Sample Queries Available in Download Center
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 controlthe other criteria. The equivalent SQL Where condition is as follows:
   Where Region Like Forms![Pick Employees]!Region & "*"   Or Forms![Pick Employees]!Region Is Null				
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.
queries Qrysmp00 exe
Properties

Article ID: 209261 - Last Review: 07/15/2004 14:43:00 - Revision: 1.1

  • Microsoft Access 2000 Standard Edition
  • kbhowto KB209261
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