Database Constraints
When defining your entities, you can specify their Identifiers and the relationships they have with other entities of your eSpace, through Reference Attributes.
In database terminology, the Identifier of an entity corresponds to its Primary Key and the Reference Attributes correspond to Foreign keys. OutSystems automatically creates the necessary database constraints as explained below.
Primary Key
When you define an attribute as an Identifier, the database creates a Primary Key constraint, prefixed as OSPRK, as presented below.
SQL Server
CONSTRAINT OSPRK_<internal name> PRIMARY KEY CLUSTERED (<attribute>)
Oracle
CONSTRAINT OSPRK_<internal name> PRIMARY KEY (<attribute>)
MySql
CONSTRAINT OSPRK_<internal name> PRIMARY KEY (<attribute>)
Foreign Keys
Only attributes where the Delete Rule property is set to Protected or Delete create a Foreign key database constraint. These constraints, prefixed as OSFRK, depend on this Delete Rule property, as explained below.
Protected
CONSTRAINT OSFRK_<internal name> FOREIGN KEY (<reference attribute>) REFERENCES <Entity>(<attribute>)
Delete
CONSTRAINT OSFRK_<internal name> FOREIGN KEY (<reference attribute>) REFERENCES <Entity>(<attribute>) ON DELETE CASCADE