Introduced in version 2.1 (Released November 3rd)
From Mendix version 7.1.0, Mendix recommends setting the uniqueness validation to Database in the Project Runtime Settings, to prepare your app for future versions of Mendix, in which this setting will be the default.
Mendix shares: “The effect of selecting Database is that when you deploy a model with unique validation rules on attributes (existing rules or new rules), all the existing objects for the affected entity will be checked for the uniqueness of the attribute.”
Read more about the uniqueness validation constraint in the Mendix documentation.
Non-compliant example:
Compliant example:
In Mendix 8 projects, open the Project Settings, go to Runtime, and set the Uniqueness validation to Database.