Pattern Matching in Neo4j - Neo4j Essentials - page 91

Working with the WHERE clause
WHERE , as the name suggests, is used to filter the given set of results.
Let's consider our movie dataset and take an example where we need to fetch all relation-
ships that have some value of attribute Role , so our Cypher query would be:
MATCH (n)-[r]-() where r.Role is NOT NULL return n,r;
Another example would be where we want a count of relationships for a particular node,
which does have a value of attribute Role :
MATCH (n)-[r]-() where r.Role is NOT NULL return n,count(r);
We could also consider an example where we want only those nodes that have count
(r) is greater than 1:
MATCH (n)-[r]-() WITH n, count(r) AS countRel
WHERE countRel>1 return n,countRel;
See the usage of the WITH clause in the preceding statement, which is used to introduce the
aggregate function count(r) for counting the relationships for all nodes within our data-
base.
WITH is like the event horizon—it is a barrier between a plan and the finished execution of
that plan. Apart from the aggregate functions, WITH can also be used to chain together two
reading query parts. For example, let's assume that we need to get the count of Movie for
all Artist that are related to Movie by ACTED_IN relationship, but we should consider
only for those Artist that are linked to movies by the DIRECTED relationship:
MATCH (m:Movie)<-[r:ACTED_IN]-(a:Artist)-[d:DIRECTED]->(m)
WITH a
MATCH (a)-[:ACTED_IN]->(m1:Movie)
WITH a,count( DISTINCT m1) as TotalMovies
return a.Name as Artist,TotalMovies;
In the preceding query, we have chained two reading query parts: the first one does the fil-
tering and gets the Artist that are related to Movie by DIRECTED and ACTED_IN re-
lationships, and the second one counts the movies of the selected Artist that are related