When creating Entities, you can guarantee the uniqueness of an Integer attribute by creating a sequential attribute. Most times this is useful for primary key attributes, since it's an easy way to ensure that each record is unique.
To create a sequential attribute, simply set the IsAutoNumber property of that attribute, to Yes.
You can only have one sequential attribute per entity, and for Static Entities only the Identifier attribute (Id), can be sequential.
When using the Create<Entity> action to insert new records on the database, you can leave the value for the auto number attribute without any value.
If you provide a value for that attribute, OutSystems Platform ignores it, and its value is calculated by the database. This ensures the value is sequential and unique.
Attribute Properties | Attributes Definition | Entity Definition | Auto Numbers in Database