R – Does NHibernate HQL support the UNION ALL keyword

hqlnhibernateunion-all

After extensive googling, I still can't find a definitive answer to this question. Some old articles/blog posts I've seen say not at all. Some say yes if the underling database supports it. Which is it? I asked on the nhusers group with no answer so far. Any help would be appreciated.

Best Solution

NHibernate does not support union. There is always one type in a result.

What you can do is a query to a base class or interface. NHibernate will perform a union to get all the values from all tables where the entities are mapped to.

There is also the union-subclass mapping strategy, which also implies that there is a base class or interface.

UNION Example:

SELECT 'foo' AS bar UNION SELECT 'foo' AS bar

Result:

+-----+
| bar |
+-----+
| foo |
+-----+
1 row in set (0.00 sec)

UNION ALL example:

SELECT 'foo' AS bar UNION ALL SELECT 'foo' AS bar

Result:

+-----+
| bar |
+-----+
| foo |
| foo |
+-----+
2 rows in set (0.00 sec)

R – Doesn’t NHibernate HQL support “with” keyword

Unfortunately, this is not supported in NHibernate. It was first requested in 2005 and is by far the most popular requested feature.

Best Solution

Related Solutions

Sql – the difference between UNION and UNION ALL

UNION Example:

UNION ALL example:

R – Doesn’t NHibernate HQL support “with” keyword

Related Question