HQL中的Linq“ .any”等效项

Question

I have a NHibernate Linq query and I need to translate it to HQL:

var result = Conexion.Session.Query<Person>();
result = result.Where(p => p.addresses.Any(a => a.City.Name == "mycity"));

Returns the people who have at least one adress in the city "MyCity"

How I can translate the "any" clause to "HQL sintax"?

Thanks.

Answer 1

This is the HQL equivalent:

select p 
from Person p
join p.addresses a
join a.city c
where c.name = :cityName

The any is simply resolved by the one-to-many join where condition.

If there are multiple addresses within the same City, to remove Person entity duplicates, you need to use distinct :

select distinct p 
from Person p
join p.addresses a
join a.city c
where c.name = :cityName

or

select distinct p 
from Address a 
join fetch a.person p 
join a.city c 
where c.name = :cityName

Answer 2

To replicate the SQL generated by:

var result = Conexion.Session.Query<Person>();
result = result.Where(p => p.addresses.Any(a => a.City.Name == "mycity"));

we have to do it like this:

var hql = "SELECT p FROM Person p WHERE EXISTS "
          + "(SELECT a FROM Address a "
          + "  LEFT JOIN a.City c "
          + "  WHERE p = a.Person " 
          + "    AND c.Name = 'mycity') ";

mycity could be even parameter:

var hql = "SELECT p FROM Person p WHERE EXISTS "
          + "(SELECT a FROM Address a "
          + "  LEFT JOIN a.City c "
          + "  WHERE p = a.Person " 
          + "    AND c.Name = :mycity) ";

var result = Conexion.Session.CreateQuery(hql)
        .SetParameter("mycity", "...")
        .List<Person()

That will work, in case, that Address has a back reference to Person , because that is part of condition WHERE p = a.Person

In case, that mapping contains only way from Person to Address, hql must be like this:

var hql = "SELECT p FROM Person p WHERE EXISTS "
          + "(SELECT p2 FROM Person p2 "
          + "  LEFT JOIN p2.addresses a "
          + "  LEFT JOIN a.City c "
          + "  WHERE p = p2 " 
          + "    AND c.Name = :mycity) ";

That will work even if the referenc from address to person is missing