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| -rw-r--r-- | cypher.html.markdown | 81 |
1 files changed, 51 insertions, 30 deletions
diff --git a/cypher.html.markdown b/cypher.html.markdown index 6efc0cec..2b8e9ac8 100644 --- a/cypher.html.markdown +++ b/cypher.html.markdown @@ -11,34 +11,37 @@ This tutorial assumes that you already know graph concepts like nodes and relati [Read more here.](https://neo4j.com/developer/cypher-query-language/) -`// There is just single-line comments in Cypher` - - - Nodes --- **Represents a record in a graph.** -**`()`** It's an empty *node*, to indicate that there is a *node*, but it's not relevant for the query. +```()``` +It's an empty *node*, to indicate that there is a *node*, but it's not relevant for the query. -**`(n)`** It's a *node* refered by the variable **n**, reusable in the query. It begins with lowercase and uses camelCase. +```(n)``` +It's a *node* refered by the variable **n**, reusable in the query. It begins with lowercase and uses camelCase. -**`(p:Person)`** You can add a *label* to your node, here **Person**. It's like a type / a class / a category. It begins with uppercase and uses camelCase. +```(p:Person)``` +You can add a *label* to your node, here **Person**. It's like a type / a class / a category. It begins with uppercase and uses camelCase. -**`(p:Person:Manager)`** A node can have many *labels*. +```(p:Person:Manager)``` +A node can have many *labels*. -**`(p:Person {name : 'Théo Gauchoux', age : 22})`** A node can have some *properties*, here **name** and **age**. It begins with lowercase and uses camelCase. +```(p:Person {name : 'Théo Gauchoux', age : 22})``` +A node can have some *properties*, here **name** and **age**. It begins with lowercase and uses camelCase. The types allowed in properties : -* Numeric -* Boolean -* String -* List of previous primitive types -**Warning : there isn't datetime property in Cypher ! You can use String with a specific pattern or a Numeric from a specific date.** + - Numeric + - Boolean + - String + - List of previous primitive types -**`p.name`** You can access to a property with the dot style. +*Warning : there isn't datetime property in Cypher ! You can use String with a specific pattern or a Numeric from a specific date.* + +```p.name``` +You can access to a property with the dot style. Relationships (or Edges) @@ -46,13 +49,17 @@ Relationships (or Edges) **Connects two nodes** -**`[:KNOWS]`** It's a *relationship* with the *label* **KNOWS**. It's a *label* as the node's label. It begins with uppercase and use UPPER_SNAKE_CASE. +```[:KNOWS]``` +It's a *relationship* with the *label* **KNOWS**. It's a *label* as the node's label. It begins with uppercase and use UPPER_SNAKE_CASE. -**`[k:KNOWS]`** The same *relationship*, refered by the variable **k**, reusable in the query, but it's not necessary. +```[k:KNOWS]``` +The same *relationship*, refered by the variable **k**, reusable in the query, but it's not necessary. -**`[k:KNOWS {since:2017}]`** The same *relationship*, with *properties* (like *node*), here **since**. +```[k:KNOWS {since:2017}]``` +The same *relationship*, with *properties* (like *node*), here **since**. -**`[k:KNOWS*..4]`** It's a structural information to use in a *path* (seen later). Here, **\*..4** says "Match the pattern, with the relationship **k** which be repeated between 1 and 4 times. +```[k:KNOWS*..4]``` +It's a structural information to use in a *path* (seen later). Here, **\*..4** says "Match the pattern, with the relationship **k** which be repeated between 1 and 4 times. Paths @@ -60,13 +67,17 @@ Paths **The way to mix nodes and relationships.** -**`(a:Person)-[:KNOWS]-[b:Person]`** A path describing that **a** and **b** know each other. +```(a:Person)-[:KNOWS]-[b:Person]``` +A path describing that **a** and **b** know each other. -**`(a:Person)-[:MANAGES]->[b:Person]`** A path can be directed. This path describes that **a** is the manager of **b**. +```(a:Person)-[:MANAGES]->[b:Person]``` +A path can be directed. This path describes that **a** is the manager of **b**. -**`(a:Person)-[:KNOWS]-[b:Person]-[:KNOWS]-[c:Person]`** You can chain multiple relationships. This path describes the friend of a friend. +```(a:Person)-[:KNOWS]-[b:Person]-[:KNOWS]-[c:Person]``` +You can chain multiple relationships. This path describes the friend of a friend. -**`(a:Person)-[:MANAGES]->[b:Person]-[:MANAGES]->[c:Person]`** A chain can also be directed. This path describes that **a** is the boss of **b** and the big boss of **c**. +```(a:Person)-[:MANAGES]->[b:Person]-[:MANAGES]->[c:Person]``` +A chain can also be directed. This path describes that **a** is the boss of **b** and the big boss of **c**. Patterns often used (from Neo4j doc) : @@ -85,6 +96,7 @@ path = shortestPath( (user)-[:KNOWS*..5]-(other) ) ``` + Create queries --- @@ -148,6 +160,7 @@ WHERE a.name = "Jacquie" AND b.name = "Michel" CREATE (a)-[:KNOWS]-(b) ``` + Update queries --- @@ -179,6 +192,7 @@ WHERE p.name = "Théo Gauchoux" SET p:Internship ``` + Delete queries --- @@ -212,17 +226,24 @@ DELETE n, r ``` *Seriously, it's the `rm -rf /` of Cypher !* + Other useful clauses --- -**`PROFILE`** Before a query, show the execution plan of it. -**`COUNT(e)`** Count entities (nodes or relationships) matching **e**. -**`LIMIT x`** Limit the result to the x first results. +```PROFILE``` +Before a query, show the execution plan of it. + +```COUNT(e)``` +Count entities (nodes or relationships) matching **e**. + +```LIMIT x``` +Limit the result to the x first results. + Special hints --- -* You can execute a Cypher script stored in a **.cql** file directly in Neo4j (it's an import). However, you can't have multiple statements in this file (separed by **;**). -* Use the Neo4j shell to write Cypher, it's really awesome. -* The Cypher will be the standard query language for all graph databases (known as **OpenCypher**). - +- There is just single-line comments in Cypher, with double-slash : // Comments +- You can execute a Cypher script stored in a **.cql** file directly in Neo4j (it's an import). However, you can't have multiple statements in this file (separed by **;**). +- Use the Neo4j shell to write Cypher, it's really awesome. +- The Cypher will be the standard query language for all graph databases (known as **OpenCypher**). |