➡️Creating Cascading Combo Boxes in Microsoft Access
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Access Database: Cascading Combo Boxes Study Guide
What is a cascading combo box in Microsoft Access?
A cascading combo box is a pair of dropdown lists where the options available in the second list are filtered based on the selection made in the first list. This creates a dependent relationship between the two combo boxes, allowing for more specific and relevant data entry.
How does a cascading combo box function?
When a user selects an item from the first combo box, an event is triggered. This event tells Access to requery the second combo box, updating its list of options to include only those related to the selection made in the first combo box.
What is the primary benefit of using cascading combo boxes?
The main advantage of using cascading combo boxes is to streamline data entry. By presenting filtered options in the second combo box, users are guided towards selecting relevant data, which can improve accuracy and efficiency.
How do you create the first combo box in a cascading pair?
The first combo box needs to be configured to display the primary categories or filtering criteria. This is typically done by setting its Row Source property to a query that retrieves the unique values from the relevant field (e.g., categories from a products table). Using the "Unique Values" property in the query builder is crucial to avoid duplicate entries in the dropdown.
How is the second combo box configured to be dependent on the first?
The second combo box's Row Source is set to a query that retrieves the dependent data (e.g., product names) along with the filtering field (e.g., category). The key step is to add a criterion to the filtering field in the query that references the value selected in the first combo box on the form. This is done by using a syntax like Forms![YourFormName]![YourFirstComboBoxName].
What is the purpose of the After Update event for the first combo box?
The After Update event for the first combo box is essential to make the cascading functionality work dynamically. This event is triggered every time the value in the first combo box is changed. The code associated with this event tells the second combo box to "requery" itself, thereby updating its options based on the new selection in the first combo box.
What is the simple line of code needed in the After Update event to make the second combo box update?
The single line of code required is YourSecondComboBoxName.Requery. This command instructs Access to re-run the query that populates the second combo box, taking into account the current criterion which is linked to the selection in the first combo box.
Why might a cascading combo box not update correctly after initial setup?
A common reason for the second combo box not updating is forgetting to add the Requery method to the After Update event of the first combo box. Without this, Access doesn't automatically know to refresh the options in the second dropdown when a new selection is made in the first.
Quiz
What is a cascading combo box in Microsoft Access?
How are the two combo boxes in a cascading setup related?
What are the minimum components needed to start building a cascading combo box system on a form?
What property of the top combo box is used to link it to the data source of the categories?
Why is it important to set the "Unique Values" property to "Yes" in the query for the category combo box?
In the row source query for the products combo box, what fields are typically included?
How is the criteria for the products combo box set up to filter based on the category selection?
What is the purpose of the "Forms!dropdowns!category" expression used in the criteria?
Which event is used on the category combo box to trigger an update in the products combo box?
What single line of VBA code is used in the "After Update" event of the category combo box to refresh the products combo box?
Quiz Answer Key
A cascading combo box is a setup where the options in one combo box are filtered based on the selection made in another combo box.
The options in the second combo box are dependent on and dynamically updated by the selection in the first combo box.
The minimum components are a form and two combo box controls added to the form.
The "Row Source" property of the top combo box is used to link it to the data source of the categories.
Setting "Unique Values" to "Yes" ensures that only distinct categories are listed in the category combo box, avoiding duplicate entries.
The row source query for the products combo box typically includes the product name and the category field.
The criteria for the products combo box is set using an expression that refers to the value selected in the category combo box on the form.
This expression refers to the "category" field on the form named "dropdowns" and is used as the criteria to filter the products shown.
The "After Update" event on the category combo box is used to trigger an update in the products combo box whenever a new category is selected.
The line of code products.Requery is used in the "After Update" event to refresh the products combo box.
Glossary of Key Terms
Cascading Combo Box: A set of two or more combo boxes where the options available in a subsequent combo box are filtered based on the selection made in a preceding one.
Combo Box: A control on a form that allows a user to select a value from a list or type a new value.
Row Source: The property of a control (like a combo box or list box) that specifies the data source (table, query, or SQL statement) from which the control gets its list of values.
Criteria: A condition or set of conditions used to filter data in a query, form, or report.
Unique Values: A property in a query that, when set to "Yes," displays only distinct or non-duplicate values in the result set.
Forms Collection: A collection in Microsoft Access that contains all the currently open forms.
Event: An action recognized by an object (like a form or control) that a macro or Visual Basic event procedure can respond to.
After Update Event: An event that occurs after data in a control or record is changed and the control or record is updated.
Requery: An action or method that updates the data in a specified control (like a combo box or list box) or the records in the underlying record source of a form or report.
Design View: A view in Microsoft Access used to design or modify the structure of database objects like tables, queries, forms, and reports.
Form View: A view in Microsoft Access used to display and interact with data through a form.
Code Builder: A tool in Microsoft Access that allows you to write and edit VBA code for event procedures and modules.
Control Source: The property of a bound control on a form or report that specifies the field in the underlying table, query, or SQL statement from which the control gets or stores data.
