O Firestore oferece uma poderosa funcionalidade de consulta para especificar quais
documentos você quer recuperar em uma coleção. Essas consultas também podem ser usadas com get()
ou addSnapshotListener()
, conforme descrito em Receber dados.
Ordenar e limitar dados
Por padrão, uma consulta recupera todos os documentos que atendem a ela em ordem crescente por ID. Use orderBy()
para especificar a ordem de classificação dos dados e limit()
para limitar o número de documentos recuperados.
Por exemplo, para consultar as três primeiras cidades em ordem alfabética, use:
Web
citiesRef.orderBy("name").limit(3);
Swift
citiesRef.order(by: "name").limit(to: 3)
Objective-C
[[citiesRef queryOrderedByField:@"name"] queryLimitedTo:3];
Java
Android
citiesRef.orderBy("name").limit(3);
Kotlin+KTX
Android
citiesRef.orderBy("name").limit(3)
Java
Query query = cities.orderBy("name").limit(3); Query query = cities.orderBy("name").limitToLast(3);
Python
db.collection(u'cities').order_by(u'name').limit(3).stream()
C++
cities_ref.OrderBy("name").Limit(3);
Node.js
const firstThreeRes = await citiesRef.orderBy('name').limit(3).get();
Go
query := cities.OrderBy("name", firestore.Asc).Limit(3)
PHP
$query = $citiesRef->orderBy('name')->limit(3);
Unity
Query query = citiesRef.OrderBy("Name").Limit(3);
C#
Query query = citiesRef.OrderBy("Name").Limit(3);
Ruby
query = cities_ref.order("name").limit(3)
Para ver as três últimas cidades, classifique em ordem decrescente:
Web
citiesRef.orderBy("name", "desc").limit(3);
Swift
citiesRef.order(by: "name", descending: true).limit(to: 3)
Objective-C
[[citiesRef queryOrderedByField:@"name" descending:YES] queryLimitedTo:3];
Java
Android
citiesRef.orderBy("name", Direction.DESCENDING).limit(3);
Kotlin+KTX
Android
citiesRef.orderBy("name", Query.Direction.DESCENDING).limit(3)
Java
Query query = cities.orderBy("name", Direction.DESCENDING).limit(3);
Python
cities_ref = db.collection(u'cities') query = cities_ref.order_by( u'name', direction=firestore.Query.DESCENDING).limit(3) results = query.stream()
C++
cities_ref.OrderBy("name", Query::Direction::kDescending).Limit(3);
Node.js
const lastThreeRes = await citiesRef.orderBy('name', 'desc').limit(3).get();
Go
query := cities.OrderBy("name", firestore.Desc).Limit(3)
PHP
$query = $citiesRef->orderBy('name', 'DESC')->limit(3);
Unity
Query query = citiesRef.OrderByDescending("Name").Limit(3);
C#
Query query = citiesRef.OrderByDescending("Name").Limit(3);
Ruby
query = cities_ref.order("name", "desc").limit(3)
Além disso, também é possível ordenar por vários campos. Por exemplo, se você quiser ordenar por estado e, em cada ordenação por estado, ordenar por população em ordem decrescente:
Web
citiesRef.orderBy("state").orderBy("population", "desc");
Swift
citiesRef .order(by: "state") .order(by: "population", descending: true)
Objective-C
[[citiesRef queryOrderedByField:@"state"] queryOrderedByField:@"population" descending:YES];
Java
Android
citiesRef.orderBy("state").orderBy("population", Direction.DESCENDING);
Kotlin+KTX
Android
citiesRef.orderBy("state").orderBy("population", Query.Direction.DESCENDING)
Java
Query query = cities.orderBy("state").orderBy("population", Direction.DESCENDING);
Python
cities_ref = db.collection(u'cities') cities_ref.order_by(u'state').order_by( u'population', direction=firestore.Query.DESCENDING)
C++
cities_ref.OrderBy("state").OrderBy("name", Query::Direction::kDescending);
Node.js
const byStateByPopRes = await citiesRef.orderBy('state').orderBy('population', 'desc').get();
Go
query := client.Collection("cities").OrderBy("state", firestore.Asc).OrderBy("population", firestore.Desc)
PHP
$query = $citiesRef->orderBy('state')->orderBy('population', 'DESC');
Unity
Query query = citiesRef.OrderBy("State").OrderByDescending("Population");
C#
Query query = citiesRef.OrderBy("State").OrderByDescending("Population");
Ruby
query = cities_ref.order("state").order("population", "desc")
É possível combinar filtros where()
com orderBy()
e limit()
. No exemplo a seguir, as consultas definem um limite para população, ordenam por esse valor em ordem crescente e retornam apenas os primeiros resultados que excedem o limite:
Web
citiesRef.where("population", ">", 100000).orderBy("population").limit(2);
Swift
citiesRef .whereField("population", isGreaterThan: 100000) .order(by: "population") .limit(to: 2)
Objective-C
[[[citiesRef queryWhereField:@"population" isGreaterThan:@100000] queryOrderedByField:@"population"] queryLimitedTo:2];
Java
Android
citiesRef.whereGreaterThan("population", 100000).orderBy("population").limit(2);
Kotlin+KTX
Android
citiesRef.whereGreaterThan("population", 100000).orderBy("population").limit(2)
Java
Query query = cities.whereGreaterThan("population", 2500000L).orderBy("population").limit(2);
Python
cities_ref = db.collection(u'cities') query = cities_ref.where( u'population', u'>', 2500000).order_by(u'population').limit(2) results = query.stream()
C++
cities_ref.WhereGreaterThan("population", FieldValue::Integer(100000)) .OrderBy("population") .Limit(2);
Node.js
const biggestRes = await citiesRef.where('population', '>', 2500000) .orderBy('population').limit(2).get();
Go
query := cities.Where("population", ">", 2500000).OrderBy("population", firestore.Desc).Limit(2)
PHP
$query = $citiesRef ->where('population', '>', 2500000) ->orderBy('population') ->limit(2);
Unity
Query query = citiesRef .WhereGreaterThan("Population", 2500000) .OrderBy("Population") .Limit(2);
C#
Query query = citiesRef .WhereGreaterThan("Population", 2500000) .OrderBy("Population") .Limit(2);
Ruby
query = cities_ref.where("population", ">", 2_500_000).order("population").limit(2)
No entanto, se você tiver um filtro com uma comparação de intervalos (<
, <=
, >
, >=
), seu primeiro pedido deve estar no mesmo campo. Consulte a lista de orderBy()
limitações abaixo.
Limitações
Observe as seguintes restrições para cláusulas orderBy()
:
- Uma cláusula
orderBy()
também filtra a existência dos campos fornecidos. O conjunto de resultados não incluirá documentos que não contenham os campos fornecidos. -
Se você incluir um filtro com uma comparação de intervalos (
<
,<=
,>
,>=
), sua primeira classificação precisará estar no mesmo campo:Válido: filtro de intervalo e
orderBy
no mesmo campoWeb
citiesRef.where("population", ">", 100000).orderBy("population");
Swift
citiesRef .whereField("population", isGreaterThan: 100000) .order(by: "population")
Objective-C
[[citiesRef queryWhereField:@"population" isGreaterThan:@100000] queryOrderedByField:@"population"];
Java
AndroidcitiesRef.whereGreaterThan("population", 100000).orderBy("population");
Kotlin+KTX
AndroidcitiesRef.whereGreaterThan("population", 100000).orderBy("population")
Java
Query query = cities.whereGreaterThan("population", 2500000L).orderBy("population");
Python
cities_ref = db.collection(u'cities') query = cities_ref.where( u'population', u'>', 2500000).order_by(u'population') results = query.stream()
Node.js
citiesRef.where('population', '>', 2500000).orderBy('population');
Go
query := cities.Where("population", ">", 2500000).OrderBy("population", firestore.Asc)
PHP
$query = $citiesRef ->where('population', '>', 2500000) ->orderBy('population');
Unity
Query query = citiesRef .WhereGreaterThan("Population", 2500000) .OrderBy("Population");
C#
Query query = citiesRef .WhereGreaterThan("Population", 2500000) .OrderBy("Population");
Ruby
query = cities_ref.where("population", ">", 2_500_000).order("population")
Inválido: filtro de intervalo e primeiro
orderBy
em campos diferentesWeb
citiesRef.where("population", ">", 100000).orderBy("country");
Swift
citiesRef .whereField("population", isGreaterThan: 100000) .order(by: "country")
Objective-C
[[citiesRef queryWhereField:@"population" isGreaterThan:@100000] queryOrderedByField:@"country"];
Java
AndroidcitiesRef.whereGreaterThan("population", 100000).orderBy("country");
Kotlin+KTX
AndroidcitiesRef.whereGreaterThan("population", 100000).orderBy("country")
Java
Query query = cities.whereGreaterThan("population", 2500000L).orderBy("country");
Python
cities_ref = db.collection(u'cities') query = cities_ref.where(u'population', u'>', 2500000).order_by(u'country') results = query.stream()
C++
// BAD EXAMPLE -- will crash the program: cities_ref.WhereGreaterThan("population", FieldValue::Integer(100000)) .OrderBy("country");
Node.js
citiesRef.where('population', '>', 2500000).orderBy('country');
Go
// Note: This is an invalid query. It violates the constraint that range // and order by are required to be on the same field. query := cities.Where("population", ">", 2500000).OrderBy("country", firestore.Asc)
PHP
$invalidRangeQuery = $citiesRef ->where('population', '>', 2500000) ->orderBy('country');
Unity
Query query = citiesRef .WhereGreaterThan("Population", 2500000) .OrderBy("Country");
C#
Query query = citiesRef .WhereGreaterThan("Population", 2500000) .OrderBy("Country");
Ruby
query = cities_ref.where("population", ">", 2_500_000).order("country")
- Não é possível realizar sua consulta por qualquer campo incluído em uma cláusula de igualdade (
=
) ouin
.