I want to implement the following SQL query with QueryDSL:
SELECT
*
FROM
a
ORDER BY (
SELECT
COUNT(*)
FROM
b
WHERE
b.a_id = a.id
AND b.c = 1) DESC
If I omit the criteria "b.c = 1", it's quite easy:
selectFrom(a).orderBy(a.bs.size().desc());
But I can't find a way (simple or not) to include a criteria in the subquery.
I want my QueryDSL query to return a List<A> and not Tuple, if possible.
Thanks in advance !
Related
How to create HQL query "select new map(A.a1, B.b1) from A left join B on A.a2=B.b2" where B could not exist? Now it returns correct result only when B exists
Sorry. It was my fault. Incorrect condition in query: " where B.b3 = smth"
I have a query where i used WITH clause to generate results.
WITH employee AS (SELECT * FROM Employees)
SELECT * FROM employee WHERE ID < 20
UNION ALL
SELECT * FROM employee WHERE Sex = 'M'
Could you please any one let me know how to write this query in hibernate using criteria specially when with clause present in query.
First, you've dramatically over-complicated your SQL. Here's how your query should look in pure SQL:
SELECT * FROM Employees WHERE ID < 20 or Sex = 'M'
Next, assuming you have a Hibernate entity (let's call it Employee.java for now), your HQL equivalent would be:
from Employee e where e.id < 20 or e.sex = 'M'
To do it with a Criteria, you'd do the following:
final Criteria criteria = getSession().createCriteria(Employee.class);
criteria.add(Restrictions.or(
Restrictions.lt("id", 20),
Restrictions.eq("sex", "M")
)
);
criteria.list();
How can I write a query using window functions and selecting all fields in QueryDSL?
In the docs there is an example like this:
query.from(employee)
.list(SQLExpressions.rowNumber()
.over()
.partitionBy(employee.name)
.orderBy(employee.id));
but I need to generate a query like:
SELECT * FROM
(SELECT employee.name, employee.id, row_number()
over(partition BY employee.name
ORDER BY employee.id)
FROM employee) AS sub
WHERE row_number = 1
And is it possible to do it with JPAQuery?
JPAQuery supports only the expressivity of JPQL, so window functions are not supported, but paging should work using
query.from(employee).orderBy(employee.id).limit(1)
In case you need to use window functions and you need employee.name and employee.id out this should work
NumberExpression<Long> rowNumber = SQLExpressions.rowNumber()
.over()
.partitionBy(employee.name)
.orderBy(employee.id).as("rowNumber");
query.select(employee.name, employee.id)
.from(SQLExpressions.select(employee.name, employee.id, rowNumber)
.from(employee).as(employee))
.where(Expressions.numberPath(Long.class, "rowNumber").eq(1L))
.fetch();
As written by #timo Window functions (rank, row_number) are not supported by JPQL (JPA 2.1 version) and hence by JPAQuery (QueryDsl Jpa 4.1.4).
You can however rewrite your query so that is does not use rank over():
select a.* from employees a
where
(
select count(*) from employees b
where
a.department = b.department and
a.salary <= b.salary
) <= 10
order by salary DESC
This is supported by JPAQuery, it probably goes like this.
final BooleanBuilder rankFilterBuilder =
new BooleanBuilder(employee.department.eq(employee2.department));
rankFilterBuilder.and(employee.salary.loe(employee2.salary));
query.from(employee)
.where(JPAExpressions.selectFrom(employee2)
.where(rankFilterBuilder)
.select(employee2.count())
.loe(10))
.orderBy(employee.salary);
Here is my select from the database:
SELECT * FROM testlogging.employees
where
EMPLOYEE_NO in (
select EMPLOYEES_EMPLOYEE_NO from testlogging.test_logging
where ID in (
select TEST_LOGGING_ID from testlogging.test_logging_detail
where APPROVAL_LEVELS_ID = '4'
)
)
How would i do this in JPA?
SELECT e FROM Employees e ???
If you're asking for the JPA INsyntax you would do this:
SELECT e FROM Employees e where e.employee_no IN :employeelist
as well ass
query.setParameter( "employeelist" , yourlist );
and of course build yourlist accordingly. If you don't really need to parameterize the inner queries, you can disregard this and just go the straight forward route.
Cheers,
Just in case you're using the JPA Criteria metamodel queries, the IN usage goes like this
CriteriaQuery<Pet> cq = cb.createQuery(Pet.class);
Root<Pet> pet = cq.from(Pet.class);
cq.where(pet.get(Pet_.color).in("brown", "black"));
as stated at http://docs.oracle.com/javaee/6/tutorial/doc/gjivm.html
I have written two hibernate queries:
TypedQuery q = em.createQuery("SELECT user.id FROM TableOne AS user WHERE ...", Long.class);
TypedQuery q = em.createQuery("SELECT link.user_id FROM TableTwo AS link WHERE ...", Long.class);
Now, how do I merge these two queries? My return type has to be TypedQuery
the UNION statement not work on Hibernate.
So you can:
Execute first query and put in a list;
Execute second query and put in a list;
Put the result of first and second list in a unique list.
If you want to delete the duplicated value, you must do programmatically.
Completely copying answer from https://stackoverflow.com/a/3940445/929701:
You could use id in (select id from ...) or id in (select id from ...)
e.g. instead of non-working
from Person p where p.name="Joe"
union
from Person p join p.children c where c.name="Joe"
you could do
from Person p
where p.id in (select p1.id from Person p1 where p1.name="Joe")
or p.id in (select p2.id from Person p2 join p2.children c where c.name="Joe");
At least using MySQL, you will run into performance problems with the later though. It's sometimes easier to do a poor man's join on two queries instead:
// use set for uniqueness
Set<Person> people = new HashSet<Person>((List<Person>) query1.list());
people.addAll((List<Person>) query2.list());
return new ArrayList<Person>(people);
It's often better to do two simple queries than one complex one.