GQL within SQL

GoogleSQL for Spanner supports the following syntax to use GQL within SQL queries.

Language list

GRAPH_TABLE operator

FROM GRAPH_TABLE (
  property_graph_name
  multi_linear_query_statement
) [ [ AS ] alias ]

Description

Performs an operation on a graph in the FROM clause of a SQL query and then produces a table with the results.

With the GRAPH_TABLE operator, you can use the GQL syntax to query a property graph. The result of this operation is produced as a table that you can use in the rest of the query.

Definitions

• property_graph_name: The name of the property graph to query for patterns.
• multi_linear_query_statement: You can use GQL to query a property graph for patterns. For more information, see Graph query language.
• alias: An optional alias, which you can use to refer to the table produced by the GRAPH_TABLE operator elsewhere in the query.

Examples

You can use the RETURN statement to return specific node and edge properties. For example:

SELECT name, id
FROM GRAPH_TABLE(
  FinGraph
  MATCH (n:Person)
  RETURN n.name AS name, n.id AS id
);

/*-----------+
 | name | id |
 +-----------+
 | Alex | 1  |
 | Dana | 2  |
 | Lee  | 3  |
 +-----------*/

You can use the RETURN statement to produce output with graph pattern variables. These variables can be referenced outside GRAPH_TABLE. For example,

SELECT n.name, n.id
FROM GRAPH_TABLE(
  FinGraph
  MATCH (n:Person)
  RETURN n
);

/*-----------+
 | name | id |
 +-----------+
 | Alex | 1  |
 | Dana | 2  |
 | Lee  | 3  |
 +-----------*/

The following query produces an error because id isn't included in the RETURN statement, even though this property exists for element n:

SELECT name, id
FROM GRAPH_TABLE(
  FinGraph
  MATCH (n:Person)
  RETURN n.name
);

The following query produces an error because directly outputting the graph element n is not supported. Convert n to its JSON representation using the SAFE_TO_JSON for successful output.

-- Error
SELECT n
FROM GRAPH_TABLE(
  FinGraph
  MATCH (n:Person)
  RETURN n
);

SELECT SAFE_TO_JSON(n) as json_node
FROM GRAPH_TABLE(
  FinGraph
  MATCH (n:Person)
  RETURN n
);

/*---------------------------+
 | json_node                 |
 +---------------------------+
 | {"identifier":"mUZpbk...} |
 | {"identifier":"mUZpbk...} |
 | {"identifier":"mUZpbk...} |
 +--------------------------*/