密码neo4j查询中的NOT（）

Question

I am having trouble with a simple cypher query. The query is:

MATCH (u:user { google_id : 'example_user' })--(rm:room)--(a:area),
    (c:category { name : 'culture:Yoruba' })--(o:object) 
WHERE NOT (a-[:CONTAINS]->o) 
RETURN DISTINCT o.id

The "WHERE NOT.." is being ignored and I am getting back the nodes with incoming :CONTAINS relationships from the area nodes. If I take out the "NOT" function, then I correctly only get back the nodes that have this a-->o relationship.

I think I have a weak understanding of NOT()

Answer 1

Trad,

The query is returning just what you asked it to. In your example at the link, there are three areas. None of the objects are contained by the first two areas, so all three nodes are returned. If you change the RETURN line to

RETURN a.area_number, o.id

you will see this.

I don't know about your larger problem context, but if you want to know about objects that aren't in any area, then the query

MATCH (o:object)
WHERE NOT (o)<-[:CONTAINS]-()
RETURN o.id

will accomplish the task.

Grace and peace,

Jim