DROP TABLE IF EXISTS test_products;

CREATE TABLE test_products (

    product_name VARCHAR(7),

    id_country INT,

    PRIMARY KEY (product_name, id_country)

) COLLATE='utf8_general_ci' ENGINE=INNODB;

DELIMITER //

FOR i IN 1..3700 DO INSERT INTO test_products (product_name, id_country) VALUES ('product', i); END FOR; //

DELIMITER ;

SELECT p.product_name, p.id_country, hierarchy.hierarchy

FROM test_products p

LEFT JOIN (

    SELECT p2.product_name, p2.id_country, h.hierarchy, MAX(test) AS test

    FROM test_products p2

    LEFT JOIN (

        SELECT product_name, id_country, '_exactly_' AS hierarchy, 1 AS test -- removing one single character from string '_exactly_' will stop producing error

        FROM test_products

    ) h ON h.product_name = p2.product_name AND h.id_country = p2.id_country

   GROUP BY product_name, id_country, h.hierarchy

) hierarchy ON hierarchy.product_name = p.product_name AND hierarchy.id_country = p.id_country