Using DISTINCT in JPA

Question

What column does DISTINCT work with in JPA and is it possible to change it?

Here's an example JPA query using DISTINCT:

select DISTINCT c from Customer c

Which doesn't make a lot of sense - what column is the distinct based on? Is it specified on the Entity as an annotation because I couldn't find one?

I would like to specify the column to make the distinction on, something like:

select DISTINCT(c.name) c from Customer c

I'm using mySQL and Hibernate.

Answer 1

Distinct in HQL is usually needed in Joins and not in simple examples like your own.

See also http://stackoverflow.com/questions/263850/how-do-you-create-a-distinct-query-in-hql