Neo4j: Sum relationship properties where node properties equal Value A and Value B (intersection)

问题

Basically my question is: how do I sum relationship properties where there is a related nodes that have properties equal to Value A and Value B?

For example:

I have a simple DB has the following relationship:

(site)-[:HAS_MEMBER]->(user)-[:POSTED]->(status)-[:TAGGED_WITH]->(tag)

On [:TAGGED_WITH] I have a property called "TimeSpent". I can easily SUM up all the time spent for a particular day and user by using the following query:

MATCH (user)-[:POSTED]->(updates)-[r:TAGGED_WITH]->(tags)
WHERE user.name = "Josh Barker" AND updates.date = 20141120
RETURN tags.name, SUM(r.TimeSpent) as totalTimeSpent;

This returns to me a nice table with tags and associated time spent on each. (i.e. #Meeting 4.5). However, the question arises if I want to do some advanced searches and say "Show me all the meetings for ProjectA" (i.e. #Meeting #ProjectA). Basically, I am looking for a query that I can get all of the relationships where a single status has BOTH tags (and only if it has both). Then I can SUM that number up to get a count for how many meetings I spent in #ProjectA.

How do I do this?

回答1:

MATCH (updates)-[r:TAGGED_WITH]->(tag1 {name: 'Meeting'}),
      (updates)-[r:TAGGED_WITH]->(tag2 {name: 'ProjectA'})
RETURN SUM(r.TimeSpent) as totalTimeSpent, count(updates);

This should find all updates tagged with both of those things, and sum all time spent across all of those updates.

回答2:

To create a generic solution where you may want one or more tags you could use something like this, passing in the array of tags as a parameter (and using the length of the array instead of the hard coded 2.

MATCH (user)-[:POSTED]->(update)-[r:TAGGED_WITH]->(tag)
WHERE user.name = "Josh Barker" AND updates.date = 20141120 AND tag.name IN ['Meeting', 'ProjectA']
WITH update, SUM(r.TimeSpent) AS totalTimeSpent, COLLECT(tag) AS tags
WHERE LENGTH(tags) = 2
RETURN update, totalTtimeSpent

As long as tag.name is indexed, this should be fast.

Edit - Remove User constraint

MATCH (update)-[r:TAGGED_WITH]->(tag)
WHERE tag.name IN ['Meeting', 'ProjectA']
WITH update, SUM(r.TimeSpent) AS totalTimeSpent, COLLECT(tag) AS tags
WHERE LENGTH(tags) = 2
RETURN update, totalTtimeSpent

来源：https://stackoverflow.com/questions/27053509/neo4j-sum-relationship-properties-where-node-properties-equal-value-a-and-value