I understood what he meant, I have the same question.
I've blown a "merge" statement, so now I have too many nodes (with a specific label) to "DETACH DELETE" in one transaction. So I want to do an operation that in SQL I would accomplish with a "GROUP BY" -- I want to somehow match a group of nodes based on an attribute, "DETACH DELETE" each of those (in a single transaction), then iterate until all the nodes are gone.
I'm new to Cypher, and so I'm still struggling to understand the semantics of these group operators.
On a related note, is there any way to perform multiple transactions (inside a subquery or something) from the neobrowser (the tool that comes up on port 7474)?