HQL 中的 Linq“.any”等价物

Question

我有一个 NHibernate Linq 查询，我需要将它翻译成 HQL：

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

返回在“MyCity”城市中至少拥有一个地址的人

如何将“any”子句翻译成“HQL sintax”？

谢谢。

Answer 1

复制生成的 SQL：

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

我们必须这样做：

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 可以是偶数参数：

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()

如果Address 具有对Person 的反向引用，这将起作用，因为这是条件的一部分WHERE p = a.Person

如果该映射只包含从 Person 到 Address 的方式，hql 必须是这样的：

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) ";

即使从地址到人员的引用丢失也可以工作

Answer 2

这是 HQL 等价物：

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

any 简单地由一对多连接 where 条件解决。

如果同一个City内有多个地址，去除Person实体重复，需要使用distinct：

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

或

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