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 Platform 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

See Also

Define Primary Key | Create Relationships