When using Detached Criteria Builder for criteria or projection subqueries, you must use a projection. If you think about it from a SQL perspective, this makes sense. After all, we need our subquery to return a specific result (property values, a count, etc.) which will be compared to a property value on the root table (in the case of a criteria subquery), or which will be returned as a valid column value (in the case of a projection subquery).
All of the projections available for Criteria Builder are also available for Detached Criteria Builder.
Examples
Be careful when using projections and adding criterias to your query. Hibernate does not work well with projections and alias definitions, so if you want to add a criteria you must use this.yourPropertyName to tell Hibernate not to use the alias and build a correct SQL.