GRANT customer TO client_name_surname

GRANT customer TO (SELECT rolname FROM pg_roles WHERE oid=(SELECT max(oid) FROM pg_roles)); 

CREATE OR REPLACE FUNCTION create_role()
RETURNS TABLE (f TEXT, l TEXT)
AS
$$ 
BEGIN 
DROP TABLE IF EXISTS tmpCustomer;			
CREATE TEMPORARY TABLE IF NOT EXISTS tmpCustomer (c_id int, f_name TEXT, l_name TEXT);
INSERT INTO tmpCustomer
SELECT cid, fname, lname
FROM 
	(SELECT DISTINCT c.customer_id AS cid, c.first_name AS fname, c.last_name AS lname
	FROM customer c 
	INNER JOIN rental r ON c.customer_id=r.customer_id 
	INNER JOIN payment p ON c.customer_id=p.customer_id) AS subq
ORDER BY random()
LIMIT 1;

EXECUTE 'CREATE ROLE client_'||(SELECT f_name FROM tmpCustomer)||'_'||(SELECT l_name FROM tmpCustomer);

RAISE NOTICE 'Role was created for customer % %',(SELECT f_name FROM tmpCustomer), (SELECT l_name FROM tmpCustomer);
RETURN query SELECT f_name, l_name FROM tmpCustomer;
END;
$$ LANGUAGE plpgsql;

SELECT * FROM create_role();

EXECUTE 'GRANT customer TO client_'||(SELECT f_name FROM tmpCustomer)||'_'||(SELECT l_name FROM tmpCustomer);