neo4j cypher帮助文档

The Neo4j Cypher Manual v3.5

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê2

2. Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê7

3. Clauses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê74

4. Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê153

5. Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê283

6. Query tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê313

7. Execution plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê338

• Introduction — Introducing the Cypher query language.

• Syntax — Learn Cypher query syntax.

• Clauses — Reference of Cypher query clauses.

• Functions — Reference of Cypher query functions.

• Schema — Working with indexes and constraints in Cypher.

• Query tuning — Learn to analyze queries and tune them for performance.

• Execution plans — Cypher execution plans and operators.

• Deprecations, additions and compatibility — An overview of language

developments across versions.

• Glossary of keywords — A glossary of Cypher keywords, with links to other

Chapter 1. Introduction

Cypher is a declarative graph query language that allows for expressive and efficient querying and

updating of the graph. It is designed to be suitable for both developers and operations professionals.

Cypher is designed to be simple, yet powerful; highly complicated database queries can be easily

expressed, enabling you to focus on your domain, instead of getting lost in database access.

Cypher is inspired by a number of different approaches and builds on established practices for

expressive querying. Many of the keywords, such as WHERE and ORDER BY, are inspired by SQL

(http://en.wikipedia.org/wiki/SQL). Pattern matching borrows expression approaches from SPARQL

(http://en.wikipedia.org/wiki/SPARQL). Some of the list semantics are borrowed from languages such as

Haskell and Python. Cypher’s constructs, based on English prose and neat iconography, make queries

easy both to write, and to read.

later in the manual.

Here are a few clauses used to read from the graph:

•

MATCH: The graph pattern to match. This is the most common way to get data from the graph.

•

WHERE: Not a clause in its own right, but rather part of MATCH, OPTIONAL MATCH and WITH. Adds

constraints to a pattern, or filters the intermediate result passing through WITH.

•

RETURN: What to return.

Let’s see MATCH and RETURN in action.

For example, here is a query which finds a user called 'John' and 'John’s' friends (though not his direct

friends) before returning both 'John' and any friends-of-friends that are found.

Resulting in:

return only those followed users who have a 'name' property starting with 'S'.

Resulting in:

SET (and REMOVE): Set values to properties and add labels on nodes using SET and use REMOVE to

remove them.

•

MERGE: Match existing or create new nodes and patterns. This is especially useful together with

unique constraints.

1.2. Querying and updating the graph

Cypher can be used for both querying and updating your graph.

A Cypher query part can’t both match and update the graph at the same time.

Every part can either read and match on the graph, or make updates on it.