# optionalBackReferencedOn

infix fun <TargetID : Any, Target : Entity<TargetID>, REF : Any> EntityClass<TargetID, Target>.optionalBackReferencedOn(column: Column<REF>): OptionalBackReference<TargetID, Target, ID, Entity<ID>, REF>
@JvmName(name = "optionalBackReferencedOnOpt")
infix fun <TargetID : Any, Target : Entity<TargetID>, REF : Any> EntityClass<TargetID, Target>.optionalBackReferencedOn(column: Column<REF?>): OptionalBackReference<TargetID, Target, ID, Entity<ID>, REF>

Registers an optional reference as an immutable field of the parent entity class, which returns a child 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.Studentorg.jetbrains.exposed.sql.tests.shared.entities.EntityTests.StudentBiosorg.jetbrains.exposed.sql.tests.shared.entities.EntityTests.StudentBio

infix fun <TargetID : Any, Target : Entity<TargetID>> EntityClass<TargetID, Target>.optionalBackReferencedOn(table: IdTable<*>): OptionalBackReference<TargetID, Target, ID, Entity<ID>, Any>

Registers an optional reference as an immutable field of the parent entity class, which returns a child 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