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:

SELECTname,id
FROMGRAPH_TABLE(
FinGraph
MATCH(n:Person)
RETURNn.nameASname,n.idASid
);
/*-----------+
 | 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,

SELECTn.name,n.id
FROMGRAPH_TABLE(
FinGraph
MATCH(n:Person)
RETURNn
);
/*-----------+
 | 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:

SELECTname,id
FROMGRAPH_TABLE(
FinGraph
MATCH(n:Person)
RETURNn.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
SELECTn
FROMGRAPH_TABLE(
FinGraph
MATCH(n:Person)
RETURNn
);

SELECTSAFE_TO_JSON(n)asjson_node
FROMGRAPH_TABLE(
FinGraph
MATCH(n:Person)
RETURNn
);
/*---------------------------+
 | json_node |
 +---------------------------+
 | {"identifier":"mUZpbk...} |
 | {"identifier":"mUZpbk...} |
 | {"identifier":"mUZpbk...} |
 +--------------------------*/