The N+1 SELECT problem is a result of lazy loading and load on demand fetching strategy. In this case, Hibernate ends up executing N+1 SQL queries to populate a collection of N elements.
For example, if you have a List of N Items where each Item has a dependency on a collection of Bid object. Now if you want to find the highest bid for each item then Hibernate will fire 1 query to load all items and N subsequent queries to load Bid for each item.
So in order to find the highest bid for each item your application ends up firing N+1 queries.
