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Mapping partial column values using Toplink

Suppose I have a list of IDs as follows:
EmployeeID
-------
ABCD
AECD
ABDF
ACDF
ACDE
I have a need to read the distinct values from a list of codes, while selecting only the first two characters of the column.
In other words, its similar to using the following query:
SELECT DISTINCT LEFT (EmployeeID,2) FROM TABLE1
My question is how do I map such a field in TOPLINK.
Note:I have created a class for the EmployeeID, but dont have an idea of mapping a partial field.

Ok... After looking at many workarounds, I seem to have a more suited solution.
I created an object for this particular scenario (the POJO has only the field for the holding the 2 Char ID, and its getter and setter methods).
During the mapping, I mapped the above field to the DB column in question (EmployeeID in the table described above).
Now I selected "Custom Queries" for the above object and entered the following query for "Read all" tab.
SELECT DISTINCT LEFT (EmployeeID,2) AS EmploeeID FROM TABLE1
All the read all operations on the object will now return the list of distinct first 2 characters of IDs.
Welcome anyone's opinion on this.

Error occurring in Hibernate when join column is String

I have two tables that I want to join using hibernate. The join column, as represented in my model is a String (its a varchar(10) in my database). When I run the HQL query, what I see is the following error, "conversion failed when converting the varchar value 'AS00' to data type int. "AS500" is the first value of join column in the first row.
I do not know why hibernate is doing this. My join column is not an int. I have checked both models corresponding to my tables and they are both defined as Strings. Is there some kind of restriction on the data types that can be used for join columns?

Please post both your model and the hql query.
If I had to take a guess (and that's all any of us can do without specifics), I would say that your hql query does not use .setParameter and it does not have single quotes around the string value in your query... so it is trying to implicitly convert the value to int.
Example that would cause this error:
Query query = session.createQuery("from Person where name = bob");

sql java queries

I have a java object 'star' that consists of two columns, string name (the name of the star) and string List fans (the list of fans of this star). I'd like to persist this class using JPA1 or hibernate. I've done so using the annotation #collectionOfElements on the list. It works fine, and creates two tables.
Now I'd like to get all stars whose fans are 'alice' or 'bob' or 'charlie'. How can I do that in the easiest way (only one query rather than 3, and without using 'OR' statements if possible), using jpa queries (hibernate if it's a must), and without retrieving the whole list of fans ?
Thanks

The following query should help you:
select s.* from star s where s.fans.name in ('alice', 'bob', 'charlie')

HQL limit in subselect query

I want to insert foreign key of one table in another on basis of certain criteria. Structure is like
insert into CustomerResult(customer,draw) select c.idCustomer, from Customer c,Draw d where ..... and c.idCustomer in (select cc.idCustomer from Customer cc where ..... limit 10)
here i want to insert only fix no of records which fulfill certain criteria. I know hql has no limit keyword but want to implement like this. any suggestion?

I don't think that what you want to do (use limit in subquery) is directly supported by Hibernate. Have a look at these previous answers:
How to set a limit to inner query in Hibernate?
How do you do a limit query in HQL?

How to order by count() in JPA

I am using This JPA-Query:
SELECT DISTINCT e.label FROM Entity e
GROUP BY e.label
ORDER BY COUNT(e.label) DESC
I get no errors and the results are sorted almost correct but there are some values wrong (either two values are flipped or some single values are completly misplaced)
EDIT:
Adding COUNT(e.label) to my SELECT clause resolves this problem for this query.
But in a similar query which also contains a WHERE clause the problem persists:
SELECT DISTINCT e.label, COUNT(e.label) FROM Entity e
WHERE TYPE(e.cat) = :category
GROUP BY e.label
ORDER BY COUNT(e.label) DESC

You might need to include the COUNT(e.label) in your SELECT clause:
SELECT DISTINCT e.label, COUNT(e.label)
FROM Entity e
GROUP BY e.label
ORDER BY COUNT(e.label) DESC
UPDATE: Regarding the second query please read section 8.6. Polymorphic queries of the EntityManager documentation. It seems that if you make your queries in a way that requires multiple SELECTs, then the ORDER BY won't work anymore. Using the TYPE keyword seems to be such a case. A quote from the above link:
The following query would return all persistent objects:
from java.lang.Object o // HQL only
The interface Named might be implemented by various persistent classes:
from Named n, Named m where n.name = m.name // HQL only
Note that these last two queries will require more than one SQL SELECT. This means that the order by clause does not correctly order the whole result set. (It also means you can't call these queries using Query.scroll().)

For whatever reason the following style named query didn't work for me:
SELECT DISTINCT e.label, COUNT(e.label)
FROM Entity e
GROUP BY e.label
ORDER BY COUNT(e.label) DESC
It could be because I am using an old version of Hibernate. I got the order by working by using a number to choose the column to sort by like this:
SELECT DISTINCT e.label, COUNT(e.label)
FROM Entity e
GROUP BY e.label
ORDER BY 2 DESC

Can't see how the order could be incorrect. What is the incorrect result?
What is the SQL that is generated, if you try the same SQL directly on the database, does it give the same incorrect order?
What database are you using?
You could always sort in Java instead using sort().