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JPA Criteria query with inner join of aggregation

I'm trying to write a CriteriaQuery which will query latest observation for each city. City is defined by city_code field, while latest record is defined by observation_time field.
I can easily write it in a plain SQL, but I cant understand how to do it with jpa criteria api.
select distinct m.* from
(select city_code cc, max(observation_time) mo
from observations group by city_code) mx, observations m
where m.city_code = mx.cc and m.observation_time = mx.mo`

It is possible when You are open for loose efficiency.
So first let's transform our query to logical equivalent one:
select distinct m.* from observations m where
m.observation_time = (select max(inn. observation_time) from observations inn
where inn.city_code = m.city_code);
then let's translate it to JPA CriteriaQuery:
public List<Observation> maxForEveryWithSubquery() {
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Observation> query = builder.createQuery(Observation.class);
Root<Observation> observation = query.from(Observation.class);
query.select(observation);
Subquery<LocalDateTime> subQuery = query.subquery(LocalDateTime.class);
Root<Observation> observationInner = subQuery.from(Observation.class);
subQuery.where(
builder.equal(
observation.get(Observation_.cityCode),
observationInner.get(Observation_.cityCode)
)
);
Subquery<LocalDateTime> subSelect = subQuery.select(builder.greatest(observationInner.get(Observation_.observationTime)));
query.where(
builder.equal(subSelect.getSelection(), observation.get(Observation_.observationTime))
);
TypedQuery<Observation> typedQuery = entityManager.createQuery(query);
return typedQuery.getResultList();
}

Unfortunately JPA does not support sub queries in FROM clause. You need to write a native query or use framework like FluentJPA.

How select distinct value with pageable Spring data JPA?

I want to make a distinct select in my table with pagination, but it is claiming this error. Does anyone know how to solve it?
org.postgresql.util.PSQLException: ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list
#Query(value = "SELECT DISTINCT budget.* FROM budget LEFT JOIN user_budget ON budget.id = user_budget.budget_id ORDER BY budget.created DESC, ?#{#pageable}",
countQuery = "SELECT DISTINCT count(*) FROM budget LEFT JOIN user_budget ON budget.id = user_budget.budget_id",
nativeQuery = true)
public Page<Budget> findAllByfilter(Pageable pageable);

QueryDSL - order by count as alias

I'm using queryDSL to get users with some additional data from base:
public List<Tuple> getUsersWithData (final SomeParam someParam) {
QUser user = QUser.user;
QRecord record = QRecord.record;
JPQLQuery = query = new JPAQuery(getEntityManager());
NumberPath<Long> cAlias = Expressions.numberPath(Long.class, "cAlias");
return query.from(user)
.leftJoin(record).on(record.someParam.eq(someParam))
.where(user.active.eq(true))
.groupBy(user)
.orderBy(cAlias.asc())
.list(user, record.countDistinct().as(cAlias));
}
Despite it's working as desired, it generates two COUNT() in SQL:
SELECT
t0.ID
t0.NAME
to.ACTIVE
COUNT(DISTINCT (t1.ID))
FROM USERS t0 LEFT OUTER JOIN t1 ON (t1.SOME_PARAM_ID = ?)
WHERE t0.ACTIVE = true
GROUP BY t0.ID, to.NAME, t0.ACTIVE
ORDER BY COUNT(DISTINCT (t1.ID))
I want to know if it's possible to get something like this:
SELECT
t0.ID
t0.NAME
to.ACTIVE
COUNT(DISTINCT (t1.ID)) as cAlias
FROM USERS t0 LEFT OUTER JOIN t1 ON (t1.SOME_PARAM_ID = ?)
WHERE t0.ACTIVE = true
GROUP BY t0.ID, to.NAME, t0.ACTIVE
ORDER BY cAlias
I failed to understand this from documentation, please, give me some directions if it's possible.

QVehicle qVehicle = QVehicle.vehicle;
NumberPath<Long> aliasQuantity = Expressions.numberPath(Long.class, "quantity");
final List<QuantityByTypeVO> quantityByTypeVO = new JPAQueryFactory(getEntityManager())
.select(Projections.constructor(QuantityByTypeVO.class, qVehicle.tipo, qVehicle.count().as(aliasQuantity)))
.from(qVehicle)
.groupBy(qVehicle.type)
.orderBy(aliasQuantity.desc())
.fetch();
select
vehicleges0_.type as col_0_0_, count(vehicleges0_.pk) as col_1_0_
from vehicle vehicleges0_
group by vehicleges0_.type
order by col_1_0_ desc;
I did something like that, but I did count first before ordering. Look the query and the select generated.

That's a restriction imposed by SQL rather than by queryDSL.
You may try to run your suggested query in a DB console - I think it won't execute, at least not on every DB.
But I don't think this duplicated COUNT() really creates any performance overhead.

Criteria (NOT IN)

please, help me:
I have next tables:
Unit
id
name
User
id
name
Rate
unit_id
user_id
I do not understand how to create correct structure of criteria from SQL:
Code:
SELECT * FROM Unit WHERE id not in (SELECT unit_id FROM Rate WHERE user_id = 55);
I saw this answer. But I do not understand how to make Condition linked to another Table (Entity).

Looking yor tag I think you need the Criteria view of your SQL query; so assuming Unit and Rate classes:
// This is the subquery
DetachedCriteria subquery = DetachedCriteria.forClass(Rate.class)
.add(Restrictions.eq("user_id", 55))
.setProjection(Projections.id())
// This corresponds to (SELECT * FROM Unit WHERE id not in (subquery))
Criteria criteria = session
.createCriteria(Unit.class)
.add(Subqueries.notIn("id", subquery));

I don't know that IN would be the most appropriate in this case. Try an inner join to link up the tables:
SELECT * FROM Unit INNER JOIN Rate ON Rate.unit_id = Unit.id
WHERE Rate.user_id = 55

How do I rewrite this particular JPQL query with SELECT MAX() to CriteriaQuery?

I am quite new to JPA and I have encountered a problem with understanding one particular query. I have rewritten in to the CriteriaQuery but the result and the query translated to SQL is not correct.
Background situation: I have a table of store transaction (moves) and the current amount in the store is defined as a sum of all changes. Now I want to select and display the last moves as they also contain an information about the resulting amount on store.
So, this is the query in JPQL:
SELECT m FROM move m WHERE m.id = (
SELECT MAX(o.id) FROM move o WHERE (o.item = m.item AND m.cell.store = :s)
I tried to rewrite it to the following CriteriaQuery:
CriteriaBuilder builder = model.getCriteriaBuilder();
CriteriaQuery<Move> query = builder.createQuery(Move.class);
Root<Move> root = query.from(Move.class);
Subquery<Long> subquery = query.subquery(Long.class);
Root<Move> subroot = subquery.from(Move.class);
subquery.select(builder.max(subroot.get("id").as(Long.class)));
subquery.where(builder.and(
builder.equal(
subroot.get("item").get("id"),
root.get("item").get("id")),
builder.equal(
subroot.get("cell").get("store").as(Store.class),
store)));
Expression<Boolean> where = builder.equal(
root.get("id"),
subquery);
query.where(where);
return model.getList(query);
The incorrect SQL query produced is following:
SELECT t0.id, (...) FROM move t0 WHERE (t0.id = (
SELECT MAX(t1.id) FROM item t3, item t2, move t1
WHERE (((t2.id = t3.id) AND
(t1.cell_store = ?)) AND
((t2.id = t1.item_ref) AND
(t3.id = t0.item_ref))))
)
I do not understand why there is a double cross join in the subquery. Thank you for helping!