The syntax of Querydsl is similar to SQL, but the order of elements is different. Instead of the basic SELECT FROM WHERE pattern, FROM WHERE LIST is used.
Example 1
Get the cats where the name's first character is between A and B :
HQLQuery q = new HibernateQuery(session); QCat cat = new QCat("cat"); // query type List<Cat> cats = q.from(cat).where(cat.name.between("A", "B")).list(cat);
The related HQL query would be
select cat from Cat cat where cat.name between A and B
As you can see the Querydsl syntax resembles the underlying HQL query very much.
Example 2
Get the cats with kittens :
HQLQuery q = new HibernateQuery(session); QCat cat = new QCat("cat"); // query type List<Cat> cats = q.from(cat).where(cat.kittens.size().gt(0)).list(cat);
Example 3
Get the mother, mate and offspring and list them as Family instances :
HQLQuery q = new HibernateQuery(session); QCat mother= new QCat("mother"); // query type QCat mate= new QCat("mate"); QCat offspr= new QCat("offspr"); List<Family> families = q.from(mother).innerJoin(mother.mate, mate).leftJoin(mother.kittens, offspr) .list(new QFamily(mother, mate, offspr));
Alternatively you may also write this shorter as
HQLQuery q = new HibernateQuery(session); QCat mother= new QCat("mother"); // query type QCat offspr= new QCat("offspr"); List<Family> families = q.from(mother).leftJoin(mother.kittens, offspr) .list(new QFamily(mother, mother.mate;, offspr));