Neo4j Notes - Cypher Manual Chap
3 Clauses
See simpler version at this doc
See full introduction here
3.1 MATCH
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3.1.1 Intro
3.1.2 Basic node finding
Too simple, omitted.
3.1.3 Relationship basics
Too simple, omitted.
3.1.4 Relationships in depth
3.1.4.1 Relationship types with uncommon characters
MATCH (charlie:Person { name: 'Charlie Sheen' }),(rob:Person { name: 'Rob Reiner' })
CREATE (rob)-[:`TYPE
WITH SPACE`]->(charlie)
Which leads to the following graph:
Graph 2.png
3.1.4.2 Multiple relationships
MATCH (charlie { name: 'Charlie Sheen' })-[:ACTED_IN]->(movie)<-[:DIRECTED]-(director)
RETURN movie.title, director.name
3.1.4.3. Variable length relationships
using the following syntax: -[:TYPE*minHops..maxHops]→. minHops and maxHops are optional and default to 1 and infinity respectively.
MATCH (martin { name: 'Charlie Sheen' })-[:ACTED_IN*1..3]-(movie:Movie)
RETURN movie.title
result:
movie.title
"Wall Street"
"The American President"
"The American President"
3.1.4.4 Relationship variable in variable length relationships
When the connection between two nodes is of variable length, the list of relationships comprising the connection can be returned using the following syntax:
MATCH p =(actor { name: 'Charlie Sheen' })-[:ACTED_IN*2]-(co_actor)
RETURN relationships(p)
relationships(p)
[:ACTED_IN[0]{role:"Bud Fox"},:ACTED_IN[1]{role:"Carl Fox"}]
[:ACTED_IN[0]{role:"Bud Fox"},:ACTED_IN[2]{role:"Gordon Gekko"}]
3.1.4.5. Match with properties on a variable length path
MATCH (charlie:Person { name: 'Charlie Sheen' }),(martin:Person { name: 'Martin Sheen' })
CREATE (charlie)-[:X { blocked: FALSE }]->(:UNBLOCKED)<-[:X { blocked: FALSE }]-(martin)
CREATE (charlie)-[:X { blocked: TRUE }]->(:BLOCKED)<-[:X { blocked: FALSE }]-(martin)
image.png
MATCH p =(charlie:Person)-[* { blocked:false }]-(martin:Person)
WHERE charlie.name = 'Charlie Sheen' AND martin.name = 'Martin Sheen'
RETURN p
result:
p
(0)-[X,20]->(20)<-[X,21]-(1)
3.1.4.6 Zero length paths
If the path length between two nodes is zero, they are by definition the same node.
MATCH (wallstreet:Movie { title: 'Wall Street' })-[*0..1]-(x)
RETURN x
Returns the movie itself as well as actors and directors one relationship away
3.1.4.7 Named paths
MATCH p =(michael { name: 'Michael Douglas' })-->()
RETURN p
result:
p
(2)-[ACTED_IN,5]->(6)
(2)-[ACTED_IN,2]->(5)
3.1.4.8. Matching on a bound relationship
MATCH (a)-[r]-(b)
WHERE id(r)= 0
RETURN a,b
a b
Node[0]{name:"Charlie Sheen"} Node[5]{title:"Wall Street"}
Node[5]{title:"Wall Street"} Node[0]{name:"Charlie Sheen"}
3.1.5 Shortest path
3.1.5.1. Single shortest path
MATCH (martin:Person { name: 'Martin Sheen' }),(oliver:Person { name: 'Oliver Stone' }), p = shortestPath((martin)-[*..15]-(oliver))
RETURN p
3.1.5.2. Single shortest path with predicates
MATCH (charlie:Person { name: 'Charlie Sheen' }),(martin:Person { name: 'Martin Sheen' }), p = shortestPath((charlie)-[*]-(martin))
WHERE NONE (r IN relationships(p) WHERE type(r)= 'FATHER')
RETURN p
3.1.5.3. All shortest paths
MATCH (martin:Person { name: 'Martin Sheen' }),(michael:Person { name: 'Michael Douglas' }), p = allShortestPaths((martin)-[*]-(michael))
RETURN p
3.1.6. Get node or relationship by id
3.1.6.1 Node by id
3.1.6.2 Relationship by id
3.1.6.3 Multiple nodes by id
MATCH (n)
WHERE id(n) IN [0, 3, 5]
RETURN n
3.2 OPTIONAL MATCH
3.2.1 Introduction
OPTIONAL MATCH will use a null for missing parts of the pattern. OPTIONAL MATCH could be considered the Cypher equivalent of the outer join in SQL.
3.2.2 Optional Relationships
MATCH (a:Movie { title: 'Wall Street' })
OPTIONAL MATCH (a)-->(x)
RETURN x
return <null>
3.2.3 Properties on optional elements
MATCH (a:Movie { title: 'Wall Street' })
OPTIONAL MATCH (a)-->(x)
RETURN x, x.name
return <null> <null>
3.2.4. Optional typed and named relationship
MATCH (a:Movie { title: 'Wall Street' })
OPTIONAL MATCH (a)-[r:ACTS_IN]->()
RETURN a.title, r
return "Wall Street" <null>
3.4 RETURN
Too simple, omitted part content.
3.4.5. Return all elements
MATCH p =(a { name: 'A' })-[r]->(b)
RETURN *
will return two nodes, the relationship and the path used in the query.
3.4.10. Unique results
MATCH (a { name: 'A' })-->(b)
RETURN DISTINCT b
3.5 WITH
3.5.1 Introduction
Using WITH, you can manipulate the output before it is passed on to the following query parts.
Three common usage:
- to limit the number of entries that are then passed on to other
MATCHclauses. - to filter on aggregated values.
WITHis used to introduce aggregates which can then be used in predicates inWHERE. - to separate reading from updating of the graph.
3.5.2 Filter on aggregate function results
MATCH (david { name: 'David' })--(otherPerson)-->()
WITH otherPerson, count(*) AS foaf
WHERE foaf > 1
RETURN otherPerson.name
return "Anders"
3.5.3 Sort results before using collect on them
MATCH (n)
WITH n
ORDER BY n.name DESC LIMIT 3
RETURN collect(n.name)
return ["George","David","Ceasar"]
3.5.4. Limit branching of a path search
MATCH (n { name: 'Anders' })--(m)
WITH m
ORDER BY m.name DESC LIMIT 1
MATCH (m)--(o)
RETURN o.name
return
"Bossman"
"Anders"
3.6 UNWIND
Read Later
3.7 WHERE
3.7.1 Introduction
In the case of WITH and START, WHERE simply filters the results.
For MATCH and OPTIONAL MATCH on the other hand, WHERE adds constraints to the patterns described. It should not be seen as a filter after the matching is finished.
image.png
3.7.2 Basic usage
Too simple, most part omitted.
3.7.2.2 Filter on node label
To filter nodes by label, write a label predicate after the WHERE keyword using WHERE n:foo.
MATCH (n)
WHERE n:Swedish
RETURN n.name, n.age
3.7.2.6. Property existence checking
Use the exists() function to only include nodes or relationships in which a property exists.
MATCH (n)
WHERE exists(n.belt)
RETURN n.name, n.belt
3.7.3 String matching
3.7.3.1. Prefix string search using STARTS WITH
MATCH (n)
WHERE n.name STARTS WITH 'Pet'
RETURN n.name, n.age
3.7.3.2. Suffix string search using ENDS WITH
MATCH (n)
WHERE n.name ENDS WITH 'ter'
RETURN n.name, n.age
3.7.3.3. Substring search using CONTAINS
MATCH (n)
WHERE n.name CONTAINS 'ete'
RETURN n.name, n.age
3.7.3.4. String matching negation
use the NOT keyword to exclude all matches on given string
MATCH (n)
WHERE NOT n.name ENDS WITH 'y'
RETURN n.name, n.age
3.7.4 Regular expressoiins
=~
3.7.5 Using path patterns in WHERE
3.7.5.1 Filter on patterns
MATCH (timothy { name: 'Timothy' }),(others)
WHERE others.name IN ['Andy', 'Peter'] AND (timothy)<--(others)
RETURN others.name, others.age
return "Andy" 36
3.7.5.2 using NOT
3.7.5.3 Filter on patterns with properties
MATCH (n)
WHERE (n)-[:KNOWS]-({ name: 'Timothy' })
RETURN n.name, n.age
return "Andy" 36
3.7.5.4. Filter on relationship type
MATCH (n)-[r]->()
WHERE n.name='Andy' AND type(r)=~ 'K.*'
RETURN type(r), r.since
3.7.6 Lists
MATCH (a)
WHERE a.name IN ['Peter', 'Timothy']
RETURN a.name, a.age
"Timothy" 25
"Peter" 35
3.7.7 Missing properties and values
Read Later
