In GQL, a query is composed of one or more statements. Each statement is a self-contained unit that can be executed by the database. A typical GQL query begins with the MATCH statement, which is used to retrieve data from the graph.
Furthermore, a clause is a component of a statement that performs a specific function, such as WHERE for filtering. A clause on its own is not a complete instruction, but must be part of a statement.
Linear Query
A linear query refers to a query that is executed sequentially, where each statement is processed one after another without any branching or conditional logic. The result is returned in a straightforward progression.
<linear query statement> ::=
[ <query statement>... ] <result statement>
<query statement> ::=
<match statement>
| <filter statement>
| <let statement>
| <for statement>
| <order by statement>
| <limit statement>
| <skip statemenmt>
| <call statement>
<result statement> ::=
<return statement> [ <order by and page statement> ]
<order by and page statement> ::=
<order by statement>
| <order by statement> <skip statement>
| <order by statement> <limit statement>
| <order by statement> <skip statement> <limit statement>
| <skip statement>
| <skip statement> <limit clause>
| <limit clause>
Details
- Each linear query must conclude with a
<result statement>, which includes a<return statement>and may optionally includes an<order by and page statement>.- The
<order by and page statement>consists of standaloneORDER BY,SKIP, andLIMITstatements or their combinations, which must appear in this order when combined.
- The
For example, this is a linear query where the MATCH, FILTER and RETURN statements processed in a linear order:
MATCH (:User {_id: "U01"})-[:Follows]->(u:User)
FILTER u.city = "New York"
RETURN u
Query and Result Statements
Statement |
Description | Clauses |
|---|---|---|
| MATCH | Retrieves data from the graph using patterns and binds data with variables for subsequent references. | WHERE, YIELD |
| FILTER | Selects a subset of records from the intermediate result table. | |
| LET | Defines variables and adds corresponding columns to the intermediate result table. | |
| FOR | Unnest a list into individual rows. | |
| ORDER BY | Sorts records in the intermediate result or output table. | |
| LIMIT | Restricts the number of records to be retained in the intermediate result or output table. | |
| SKIP | Discards a specified number of records from the beginning of the intermediate result or output table. | |
| CALL | Invokes a system-defined procedure or inline subquery. | YIELD |
| RETURN | Specifies the columns to include in the output table. | GROUP BY |
Composite Query
A composite query combines a list of linear queries with query conjunctions.
For example, this is a composite query that uses UNION ALL to combine the results of two linear queries:
MATCH (n:Club) RETURN n
UNION ALL
MATCH (n:User) RETURN n
Learn more about Composite Query →
Advanced Linear Composition with NEXT
The NEXT statement can be used to chain multiple linear or composite query statements together, enabling more complex queries.
Learn more about NEXT →