Hi. I have the following structure:
NodeA has relationships to multiple NodeB; the relationships have a
property called 'preferred', which takes boolean values. I need to be able
to atomically change the preferred NodeB. I am doing this with Cypher on
version 1.8.
What I have now is two queries which look like this:

// reset the currently preferred, if any
start me = node({me}) match me-[r:LIKES]->t set r.preferred = false where
r.preferred = true // this might result in no relationships changed, that's
Ok - no preference yet
// set the new preferred
start me = node({me}), t = node({t}) match me-[r:LIKES]->t set r.preferred
= true

(Parameters 'me' and 't' are Nodes that I already have and don't have to
look up.)

This will be done in a single transaction so that it is atomic. However, I
have a couple of questions:

1. Is it possible to do such a thing in a single query? Is this practical?
Is it better to issue 2 simpler queries than 1 complex?
2. I would like to learn if the second query actually changed any
relationship. This is for error checking - node 't' in the second query
might not be related to 'me' at all, in which case the query would change 0
relationships. I think the easiest way for me would be to check the count
of changed relationships if I could return that, and if it is 0, node 't'
was unrelated to 'me'. How can I express this in Cypher?

Regards,
wujek