Question

I have a hibernate managed POJO with a set:

public class Book {
    private Set<Page> pages;
    public Set<Page> getPages() { return pages; }
    public void setPages(Set<Page> pages) { this.pages = pages; }
}
public class Page {
    private int pageNumber;
    public int getPageNumber() { return pageNumber; }
    public void setPageNumber(int pageNumber) { this.pageNumber = pageNumber;
}

How would I write a HQL query based on the page number? For example, return all books that have a pageNumber greater than 100?

The following does not work:

from Book where pages.pageNumber > 100

Answer 1

Use join:

select distinct b from Book b join b.pages p where p.pageNumber > 100

Without distinct it would return a separate instance of Book for each page satisfying the condition.

See also:

• 16.3. Associations and joins