What can you use a constraint function for?

A constraint function in Mendix is specifically used to filter data in XPath queries based on certain criteria, which includes working with strings and dates. This function allows developers to define conditions that retrieve only those records that meet specific requirements. By applying a constraint in an XPath query, you enable the application to pull a precise subset of data, making it a critical tool for effective data management and retrieval.

Using constraint functions in this way is fundamental to the operation of flexible and dynamic applications, ensuring that users have access to relevant data without being overwhelmed by information that does not meet their needs.

While there are other ways to manipulate data, such as summing or averaging numerical values or joining tables, these operations do not align with the purpose of a constraint function, which focuses solely on the filtration aspect in the querying process.