Cypher cannot be used in an expression— the query must exist in the FROM clause of a query. However, if the cypher query is placed in a subquery, it will behave as any SQL style query.

Using Cypher with ‘=’

When writing a cypher query that is known to return one column and one row, the ‘=’ comparison operator may be used.

SELECT t.name FROM schema_name.sql_person AS t
where t.name = (
    SELECT a
    FROM cypher('graph_name', $$
          MATCH (v)
        RETURN v.name
    $$) as (name varchar(50))
    ORDER BY name
    LIMIT 1);

Results:

Working with Postgres’s IN Clause

When writing a cypher query that is known to return one column, but may have multiple rows. The IN operator may be used.

Query:

SELECT t.name, t.age FROM schema_name.sql_person as t 
where t.name in (
    SELECT *
    FROM cypher('graph_name', $$
        MATCH (v:Person)
        RETURN v.name 
    $$) as (a agtype));

Results:

Working with the Postgres EXISTS Clause

When writing a cypher query that may have more than one column and row returned. The EXISTS operator may be used.

Query:

SELECT t.name, t.age
FROM schema_name.sql_person as t
WHERE EXISTS (
    SELECT *
    FROM cypher('graph_name', $$
      MATCH (v:Person)
        RETURN v.name, v.age
    $$) as (name agtype, age agtype)
    WHERE name = t.name AND age = t.age
);

Results:

Querying Multiple Graphs

There is no restriction to the number of graphs an SQL statement can query. Users may query multiple graphs simultaneously.

SELECT graph_1.name, graph_1.age, graph_2.license_number
FROM cypher('graph_1', $$
    MATCH (v:Person)
    RETURN v.name, v.age
$$) as graph_1(col_1 agtype, col_2 agtype, col_3 agtype)
JOIN cypher('graph_2', $$
    MATCH (v:Doctor)
    RETURN v.name, v.license_number
$$) as graph_2(name agtype, license_number agtype)
ON graph_1.name = graph_2.name

Results: