ACC2000: Showing All Records (Including Null) in a Parameter Query
ID: Q209261
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The information in this article applies to:
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, 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.
MORE INFORMATION
The following example is based on the sample database Northwind.mdb.
- 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
- 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
- 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
- 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.
- 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.
- 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
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.
Additional query words:
queries
Keywords : kbdta
Version : WINDOWS:2000
Platform : WINDOWS
Issue type : kbhowto