Nhibernate HQL Subselect queries

Question

I have the following SQL query:

select c.id
from (select id from customers) c

This query has no practical value - I simplified it greatly for the purpose of this post.

My question: is it possible have a subquery in the from clause using HQL. If not, can I perhaps query the customers first, kinda like a temp table in sql, and then use the result as the source of the next query?

thanks

Answer 1

I've run into this issue myself. Took me a while to realise that hql does not support subqueries in the from clause.

See section 14.13 in the hql documentation here.

Answer 2

Yes, it's possible.

The query above can be written in HQL as:

select Id
from Customer
where Id in (select Id from Customer)