Cypher Queries
Learning
Nodes
() or (p)
() // anonymous node (no label or variable) can refer to any node in the database
(p:Person) // using variable p and label Person
(:Technology) // no variable, label Technology
(work:Company) // using variable work and label Company
(p:Person:Mammal) // Double label
(p:Person {name:'Veronica'}) // Label with property
Relationships
Relationships are wrapped with hyphens or square brackets
--> or -[h:HIRED]->
Direction of relationship is specified with <>
(p1)-[:HIRED]->(p2) or (p1)<[:HIRED]-(p2)
Relationships have properties
-[:HIRED {type: 'fulltime'}]->
Basics
//data stored with this direction
CREATE (p:Person)-[:LIKES]->(t:Technology)
//query relationship backwards will not return results
MATCH (p:Person)<-[:LIKES]-(t:Technology)
//better to query with undirected relationship unless sure of direction
MATCH (p:Person)-[:LIKES]-(t:Technology)
Practice
Let's create a guild with channels and specific people only have access to specific channels
codium Software.List.neo4j.drawio- Node names
- User
- Channel
- Guild
- Relationships
- GuildChannel (Guild to Channel)
- Join (Users to Channel)
- MemberOf (Guild to User)
- We have Paul, Amy, Tom, and Sarah
- We have Channel's General, Admin, Ladies, and Boys for ddaemon guild
- We have a guild with Tom and Paul called GamerNight, with the Channel CSGO
wiki.software.list.neo4j.errors wiki.software.programming language.cypher.Basic Queries
// Check existing nodes and relationships
MATCH (n) RETURN n;
// Match N
MATCH (n)
DETACH DELETE n
``` cypher
CREATE (g:Guild {name:'ddaemon'})
RETURN g;
CREATE (g:Guild {name:'GamerNight'});
CREATE (u:User {name:'Paul'});
CREATE (u:User {name:'Amy'});
CREATE (u:User {name:'Tom'});
CREATE (u:User {name:'Sarah'});
CREATE (u:Channel {name:'General'});
CREATE (u:Channel {name:'CSGO'});
CREATE (u:Channel {name:'Admin'});
CREATE (u:Channel {name:'Ladies'});
CREATE (u:Channel {name:'Boys'});
MATCH (guild:Guild {name:'ddaemon'})
MATCH (channel:Channel {name:'General'})
CREATE (guild)-[:GuildChannel]->(channel);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (channel:Channel {name:'Admin'})
CREATE (guild)-[:GuildChannel]->(channel);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (channel:Channel {name:'Ladies'})
CREATE (guild)-[:GuildChannel]->(channel);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (channel:Channel {name:'Boys'})
CREATE (guild)-[:GuildChannel]->(channel);
MATCH (user:User {name:'Paul'})
MATCH (channel:Channel {name:'Boys'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Tom'})
MATCH (channel:Channel {name:'Boys'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Amy'})
MATCH (channel:Channel {name:'Ladies'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Sarah'})
MATCH (channel:Channel {name:'Ladies'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Paul'})
MATCH (channel:Channel {name:'General'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Amy'})
MATCH (channel:Channel {name:'General'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Tom'})
MATCH (channel:Channel {name:'General'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Sarah'})
MATCH (channel:Channel {name:'General'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Paul'})
MATCH (channel:Channel {name:'Admin'})
CREATE (user)-[:Join]->(channel);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (user:User {name:'Amy'})
CREATE (user)-[:MemberOf]->(guild);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (user:User {name:'Tom'})
CREATE (user)-[:MemberOf]->(guild);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (user:User {name:'Paul'})
CREATE (user)-[:MemberOf]->(guild);
MATCH (guild:Guild {name:'ddaemon'})
MATCH (user:User {name:'Sarah'})
CREATE (user)-[:MemberOf]->(guild);
MATCH (guild:Guild {name:'GamerNight'})
MATCH (user:User {name:'Paul'})
CREATE (user)-[:MemberOf]->(guild);
MATCH (guild:Guild {name:'GamerNight'})
MATCH (user:User {name:'Tom'})
CREATE (user)-[:MemberOf]->(guild);
MATCH (user:User {name:'Paul'})
MATCH (channel:Channel {name:'CSGO'})
CREATE (user)-[:Join]->(channel);
MATCH (user:User {name:'Tom'})
MATCH (channel:Channel {name:'CSGO'})
CREATE (user)-[:Join]->(channel);
//Check Exists
MATCH (user:User {name:'Tom'})
MATCH (channel:Channel {name:'CSGO'})
UPDATE (user)-[:Join]->(channel);
RETURN (user)-[:Join]->(channel)
MATCH (g:Guild {name:'hello'})
RETURN COUNT(g);
MATCH (u:Channel {name:"General"})
DELETE u;
MATCH (a)-[b]-(u:Channel {name:"General"})
RETURN a, b, u;
MATCH (a)-[b]-(u:Channel {name:"General"})
DELETE b;
MATCH (g:Guild) RETURN COUNT(g);
DELETE g
MATCH (user:User)
MATCH (guild:Guild)
MATCH (channel:Channel)
return user, channel, guild
MATCH (guild:Guild)
return guild.name
MATCH (channel:Channel)
return channel.name
MATCH (user:User)
return user.name
MATCH (guild:Guild)
return guild
MATCH (guild:Guild)
MATCH (channel:Channel)
return guild, channel
MATCH (user:User)
MATCH (channel:Channel)
return user, channel
MATCH (user:User)
MATCH (guild:Guild)
return user, guild
MATCH (channel:Channel {name:"Ladies"})-[:Join]-(user:User)
RETURN channel, user
MATCH (channel:Channel {name:"Ladies"})-[:Join]-(user:User)
RETURN user.name
MATCH (user:User)-[:MemberOf]->(guild:Guild)
RETURN user, guild
MATCH (user:User)-[:MemberOf]->(guild:Guild)
RETURN user.name, guild.name
Scratchpad
MATCH (movie:Movie)
RETURN movie.title
CREATE (g:Guild {name:'ddaemon'})-[:GuildUser]->(u:User {name:'Paul'});
CREATE (g:Guild {name:'ddaemon'})-[:GuildUser]->(u:User {name:'Amy'});
CREATE (g:Guild {name:'ddaemon'})-[:GuildUser]->(u:User {name:'Tom'});
CREATE (g:Guild {name:'ddaemon'})-[:GuildUser]->(u:User {name:'Sarah'});
CREATE (u:User {name:'ddaemon'})-[:GuildUser]->(u:User {name:'Sarah'});
CREATE INDEX ON:Guild(Tag)
CREATE CONSTRAINT ON (u:User) ASSERT u.name IS UNIQUE;
CREATE CONSTRAINT ON (u:Guild) ASSERT u.name IS UNIQUE;
CREATE CONSTRAINT ON (u:Channel) ASSERT u.name IS UNIQUE;