subform

A subform is a form embedded within another form in a user interface or data-entry application. It is used to display and manage related records from a second table or form, allowing data to be viewed and edited in the context of a parent record.

In relational database tools such as Microsoft Access, a subform is placed on a main form using a subform control. The subform shows data from a related table or form and is typically linked to the main form by master and child fields. As the user moves through the main form, the subform updates to show the related records for the current parent record. The subform can present data in form view or in a datasheet/continuous view.

Design considerations include choosing the appropriate view, correctly configuring the link fields, sizing and layout, and performance implications for large datasets. It is important to maintain referential integrity and to evaluate whether a subform is the best solution or if alternatives such as a tabbed interface or a single form with a continuous subform would be more effective.

Limitations of subforms include added interface complexity, potential performance issues with many linked records, and challenges in printing or exporting complex layouts. Accessibility and keyboard navigation should also be considered.

Common uses of subforms include displaying child data such as orders related to a customer or line items related to an invoice. The term is sometimes used interchangeably with “child form,” and the container hosting the subform is called a subform control.