Graph Query Language (GQL) is a language designed to query graph data. This page describes the high level structure of GQL.
Statement and clause
In GQL, a statement refers to a complete unit of execution, and a clause represents a modifier to statements. See the statement list for a complete list.
Working table
A working table refers to the intermediate table representing the input or output of a GQL statement.
A GQL statement receives an incoming working table and produces an outgoing working table.
The first incoming working table is a table with a single row. The last outgoing working table is returned as the query results.
Linear query statement
A linear query statement consists of multiple statements from the statement
list. It always ends with a RETURN statement.
Each statement generates intermediate results (the working table) and
then passes those results to the next statement. The output of a
linear query statement comes from the final RETURN statement.
Examples
GRAPH FinGraph
MATCH (p:Person)-[o:Owns]->(a:Account)
FILTER p.birthday < '1990-01-10'
RETURN p.name
/*------+
| name |
+------+
| Dana |
| Lee |
+------*/
Combining linear query statements with set operators
You can use a set operator to combine multiple linear query statements into one. For more information, see the syntax for the GQL set operation.
Examples
A set operator between two linear query statements with the same set of output column names and types but with different column orders is supported. For example:
GRAPH FinGraph
MATCH (p:Person)
RETURN p.name, 1 AS group_id
UNION ALL
MATCH (p:Person)
RETURN 2 AS group_id, p.name
/*------+----------+
| name | group_id |
+------+----------+
| Alex | 1 |
| Dana | 1 |
| Lee | 1 |
| Alex | 2 |
| Dana | 2 |
| Lee | 2 |
+------+----------*/
Chaining linear query statements with the NEXT statement
You can use the NEXT keyword to chain multiple linear query statements
into one.
The final linear query statement must produce non-GQL data types, but linear query statements that proceed it can produce GQL data types, such as nodes and edges.
Examples
The following is an example of a graph query chaining multiple linear query statements
using NEXT.
GRAPH FinGraph
MATCH (a:Account {is_blocked: TRUE})
RETURN a
UNION ALL
MATCH (a:Account)<-[:Owns]-(p:Person {id: 2})
RETURN a
NEXT
MATCH (a:Account)-[t:Transfers]->(oa:Account)
WITH DISTINCT oa
RETURN oa.nick_name
/*----------------+
| nick_name |
+----------------+
| Vacation Fund |
| Vacation Fund |
| Rainy Day Fund |
+----------------*/