Hybrid Query

This section explains how to use a SQL query and a Cypher query statement together as shown in the example below.

Through the SQL statement used in the RDB, table and column aggregation, statistical processing, and GDB’s Cypher syntax replace the RDB’s join operation to support better data queries.

CREATE GRAPH skai;
CREATE VLABEL dev;
CREATE (:dev {name: 'someone', year: 2015});
CREATE (:dev {name: 'somebody', year: 2016});

CREATE TABLE history (year, event)
AS VALUES (1996, 'PostgreSQL'), (2016, 'AgensGraph');

Cypher in SQL

It is possible to use a Cypher syntax inside the FROM clause to utilize the dataset of the vertices or edges stored in the graph DB as a data set in the SQL statement.

Syntex :

SELECT [column_name]
FROM ({table_name|SQLquery|CYPHERquery})
WHERE [column_name operator value];

It can be used as the following example:

SELECT n->>'name' as name 
FROM history, (MATCH (n:dev) RETURN n) as dev 
WHERE history.year > (n->>'year')::int;

Result :

  name
---------
 someone
(1 row)

SQL in Cypher

When querying the content of graph DB through Cypher syntax, it is possible to use Match and Where syntaxes for search by specific data of RDB. However, the resulting dataset in the SQL statement should be configured to return a single row of results.

Syntex :

MATCH [table_name]
WHERE (column_name operator {value|SQLquery|CYPHERquery})
RETURN [column_name];

It can be used as the following example:

MATCH (n:dev)
WHERE n.year < (SELECT year FROM history WHERE event = 'AgensGraph')
RETURN properties(n) AS n;

Result :

                 n
-----------------------------------
 {"name": "someone", "year": 2015}
(1 row)