Question

#My doubt is the partId in Product table can be null ,so if the partId is null I’m not able to see the product. If my Product Table has 11 entries and 2 entries have partId as null , Iam able to see only 9 entries

 String hql = "from " + Product.class.getName() + " bs, "
                + Part.class.getName() + " dm, "
                          + Manufacturer.class.getName() + " m where "
                          + " m.id = bs.manufacturerId and dm.id = bs.partId ";
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The ouput has to be like this
productName | PartName | Manufactuer Name

Answer 1

You need to do left joins instead of inner joins. But this is only possible if your entities are associated together instead of containing each other’s IDs.

As is, it’s plain impossible with HQL.

Given your query, you probably should have a ManyToOne between Product and Manufacturer, and a ManyToOne between Product and Part.

Also, your query would be much more readable if you didn’t concatenate class names and if you used proper alias names:

String hql = "from Product product, Part part, Manufacturer manufacturer"
             + " where manufacturer.id = product.manufacturerId"
             + " and part.id = product.partId";

Once the associations exist, the query should just be

String hql = "select product.name, part.name, manufacturer.name"
             + " from Product product"
             + " left join product.part part"
             + " left join product.manufacturer manufacturer";