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Cypher manual

Cypher is a high-level query language for the property graph data model. If you’re coming from a SQL background, it’s syntax may seem familiar. Some common analogues between SQL and Cypher are listed below:

TypeSQLCypher
QuerySELECT/FROM/WHEREMATCH/WHERE/RETURN
Data manipulationINSERT/UPDATE/DELETECREATE/SET/DELETE

The features of Cypher that are different from SQL are listed below:

  • Joins between records from different node and relationship tables are specified using a graph-like syntax.
    • MATCH (n:Person)-[:Follows]->(m:Person)
  • Special syntax, such as the Kleene star * to describe variable-length and recursive joins.
  • Cypher does not have an explicit GROUP BY like SQL does — instead, grouping is done implicitly depending on the combination of bound variables in the RETURN clause.

There are a few other differences between SQL and Cypher. Yet, like other high-level database query languages, most of its semantics can be understood as mappings to relational algebra operators for selections, joins, projections and aggregations.

Kùzu implements openCypher’s1 standard predicates and expressions. The following sections in this chapter covers all Cypher statements, clauses, expressions and functions implemented in Kùzu.

Statements vs. clauses

In Cypher, a statement is a complete query that can be executed on its own. A statement can contain one or more clauses, and can span multiple lines. The end of a statement is marked with a semicolon ;, and the query parser looks for this symbol to know when a statement is complete.

A clause is a part of a statement that performs a specific operation. For example, the MATCH clause is used to find patterns in the graph, the RETURN clause is used to specify what subset of the matched data to return, and so on.

Multi-line statements

You can execute multiple query statements sequentially in the CLI, rather than executing them one by one. To run a multi-line statements, simply end each valid statement you want to execute with a semicolon ;. For example:

MATCH (p1:Person)
WHERE p1.age <= 18
RETURN p1.name AS non_adult;


MATCH (p2:Person)
WHERE p2.age > 18
RETURN p2.name AS adult;

When you copy-paste the above blocks into the Kùzu CLI and press Enter, it will execute each block sequentially, so you don’t have to send individual queries one at a time.

Footnotes

  1. openCypher is an open-source project that formalizes the semantics, style and grammar for the Cypher query language in order to make it more compatible to be used by multiple graph database vendors. ↩