# optionalReferencedOn

infix fun <REF : Any> optionalReferencedOn(column: Column<REF?>): OptionalReference<REF, ID, T>

Registers an optional reference as a field of the child entity class, which returns a parent object of this `EntityClass`.

The reference should have been defined by the creation of a column using either `optReference()` or `reference().nullable()` on the child table.

#### Samples

org.jetbrains.exposed.sql.tests.shared.entities.EntityTests.Boardorg.jetbrains.exposed.sql.tests.shared.entities.EntityTests.Postsorg.jetbrains.exposed.sql.tests.shared.entities.EntityTests.Post

infix fun optionalReferencedOn(table: IdTable<*>): OptionalReference<Any, ID, T>

Registers an optional reference as a field of the child entity class, which returns a parent object of this `EntityClass`.

The reference should have been defined by the creation of a foreign key constraint on the child table, by using `foreignKey()`.

#### Samples

org.jetbrains.exposed.sql.tests.shared.entities.CompositeIdTableEntityTest.Publisherorg.jetbrains.exposed.sql.tests.shared.entities.CompositeIdTableEntityTest.Officesorg.jetbrains.exposed.sql.tests.shared.entities.CompositeIdTableEntityTest.Office