neo4j-cypher-manual-4.0.pdf

The Neo4j Cypher Manual v4.0

Table of Contents

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

2. Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê10

3. Clauses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê76

4. Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê157

5. Administration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê287

6. Query tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê348

7. Execution plans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ê393

This manual covers the following areas:

• Introduction — Introducing the Cypher query language.

• Syntax — Learn Cypher query syntax.

• Clauses — Reference of Cypher query clauses.

• Functions — Reference of Cypher query functions.

• Administration — Working with databases, indexes, constraints and security 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.

Chapter 1. Introduction

This section provides an introduction to the Cypher query language.

• What is Cypher?

• Neo4j databases and graphs

• Querying, updating and administering

• Transactions

• Result uniqueness

1.1. What is Cypher?

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

updating and administering 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

iconography, make queries easy, both to write and to read.

Structure

Cypher borrows its structure from SQL — queries are built up using various clauses.

Clauses are chained together, and they feed intermediate result sets between each other. For

example, the matching variables from one MATCH clause will be the context that the next clause exists

in.

The query language is comprised of several distinct clauses. These are discussed in more detail in the

chapter on Clauses.

The following are a few examples of clauses used to read from the graph:

•

Let’s see MATCH and RETURN in action.

Let’s create a simple example graph with the following query:

Figure 1. Example Graph

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:

We take a list of user names and find all nodes with names from this list, match their friends and

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.