Relation<R, F extends Fields> class final

A relationship is a query description. Constructing or selecting it performs no I/O. List results are loaded in batches on the root query's connection.

Filters, ordering, pagination, and selections return new descriptions. Each selected relationship can add queries; batching groups distinct parent keys instead of issuing one query per parent. Use a transaction when the root and its batches must share the database's configured snapshot isolation.

Constructors

Relation(Table<R, F> target, {required List<Expr<Object?>> parent, required List<ReadField<Object?>> child(F)})

Describes an equality relationship between parent and target key columns.

factory

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

any() → Expr<bool>

Builds a correlated SQL EXISTS expression for the filtered relationship.

count() → Expr<int>

Builds a correlated SQL count without fetching related rows into Dart.

every(Expr<bool?> condition(F)) → Expr<bool?>

Checks that every filtered related row makes condition SQL TRUE.

many() → Selection<List<R>>

Selects a list per parent, returning an empty list when no rows match.

none() → Expr<bool?>

Checks that no related row satisfies the where filters.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

one({ToOneStrategy strategy = ToOneStrategy.automatic}) → Selection<R?>

Selects at most one visible row, or null when no row matches.

orderBy(List<OrderTerm> order(F)) → Relation<R, F>

Replaces related-row ordering; include a stable tie breaker for pagination.

required({ToOneStrategy strategy = ToOneStrategy.automatic}) → Selection<R>

Requires one visible row while preserving the selected value's nullability.

select<S>(Selection<S> selection(F)) → Relation<S, F>

Replaces each related row's result shape without loading it.

skip(int count) → Relation<R, F>

Skips count rows per parent; batched pagination requires orderBy.

take(int count) → Relation<R, F>

Limits each parent's result to count rows; negative counts are rejected.

toString() → String

A string representation of this object.

inherited

where(Expr<bool?> predicate(F)) → Relation<R, F>

Adds a SQL predicate to the related rows, ANDed with earlier filters.

Operators

operator ==(Object other) → bool

The equality operator.

inherited