Hi all. Did some searching, couldn't find answer to total newbie question.

Hibernate version: 3.1
I'm using Eclipse and Java 5.

I have one question and one comment:
1. How do I use the count function.
2. Criticism of section 7.4.2 of Hibernate in Action


1. After reading chapter 7, I tried writing this code to get a count of records in a table that had a boolean field set to true of false:

Query query = session.createQuery(
"select count(sample.isStored = :status) from sample");
query.setEntity("status", stored);
assert query.list().size() == 1;
return (Integer)query.list().get(0);

Could someone explain a good fast way(s) to get record counts?


2. Having a bad day on a crunch project, so sorry for the orneriness, but to the authors: "how about complete code examples?" Soon this will all be tirvial for me, but look at the confusion this newbie experienced and consider how your books could be better by using complete examples.

E.g., the paragraph that talks about the sum function indicates that "the query returns a BigDecimal." So there I am looking all over the place for how exactly that works. Go ahead, insult my intelligence and show me how in your books. I'm guessing that I get back a row of Object's and then I cast the first one, etc., but the key word here is "guessing" and not "reading."

1) select count(*) from sample s where s.isStored = :status

2) I think it is difficult for authors to deal with a wide potential audience. I prefer reference books and hate the books that have large sections of very basic code samples. On the other hand I can see how this could help beginners. This provides opportunities for multiple books being successful in this topic space.

Often the wiki is a good place to look, and much of the online manual is very good.

Thank you, David, for the help and thoughtful comments despite my grumpy attitude.

Could you advise me how I could count the number of records that have no "child" records under them?

Say I have a Carton table and it has Item children that point at it. In Java, the Carton class simply has a list or set that references Item objects.

I wish to count the number of empty Carton's. Alternatively, I wish to count the Carton's that have at least one Item. Is this possible using count() in HQL?

I wish I could write something like
select count(*) from Carton c where c.items.size() == 0

or
select count(c.items) from Carton c

or?

Thanks,
BE

Your close - Hibernate includes a number of reserved word in HQL for dealing with lists. For example; You may test the size of a collection with the special property size, or the special size() function.

from Cat cat where cat.kittens.size > 0

from Cat cat where size(cat.kittens) > 0

Then its just prepending 'select count(*) '. Check out the manual for further information
http://www.hibernate.org/hib_docs/v3/reference/en/html/queryhql.html and maybe its a good idea to install the hibernate tools and try the query tool out.