Hibernate Criteria API - HAVING clause work arounds

Question

I\'ve written a query using Hibernate Criteria API to grab a summation of a particular value, now I need to be able to restrict the result to rows where that sum is greater

Answer 1

I don't know of a way for Hibernate/NHibernate to use a subquery in the FROM clause but you can use them in the WHERE clause. Apologies for any Java/Hibernate code mistakes, I am more familiar with C#/NHibernate.

DetachedCriteria subQuery = DetachedCriteria.forClass(Transaction.class);
subQuery.setProjection(Projections.sum("amount"));
subQuery.add(Expression.eqProperty("userPk", "tOuter.userPk"));

DetachedCriteria outerQuery = DetachedCriteria.forClass(Transaction.class, "tOuter");
outerQuery.setProjection(Projections.projectionList()
    .Add(Projections.sum("amount").as("sumAmount"))
    .Add(Projections.groupProperty("userPk").as("user_pk"));
outerQuery.add(Subqueries.le(50, subQuery));

This code should result in SQL similar to:

SELECT tOuter.userPk as user_pk, sum(tOuter.amount) as sumAmount
FROM transaction tOuter
WHERE 50 <= (SELECT sum(amount) FROM transaction WHERE userPk = tOuter.userPk)
GROUP BY tOuter.userPk

The disadvantage of this approach is that it calculates each of the sums twice, this might have a detrimental effect on performance depending on the amount of data involved - in which case you will want to use an HQL query which does support the HAVING clause.