Slow query on certain table(s)

Code: Select all

# Query_time: 12.909576  Lock_time: 0.000132  Rows_sent: 4  Rows_examined: 56210
SET timestamp=1487530199;
SELECT p.product_id, (SELECT AVG(rating) AS total FROM oc_review r1 WHERE r1.product_id = p.product_id AND r1.status = '1' GROUP BY r1.product_id) AS rating, (SELECT price FROM oc_product_discount pd2 WHERE pd2.product_id = p.product_id AND pd2.customer_group_id = '1' AND pd2.quantity = '1' AND ((pd2.date_start = '0000-00-00' OR pd2.date_start < NOW()) AND (pd2.date_end = '0000-00-00' OR pd2.date_end > NOW())) ORDER BY pd2.priority ASC, pd2.price ASC LIMIT 1) AS discount, (SELECT price FROM oc_product_special ps WHERE ps.product_id = p.product_id AND ps.customer_group_id = '1' AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW())) ORDER BY ps.priority ASC, ps.price ASC LIMIT 1) AS special FROM oc_product p LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = '1' AND p.status = '1' AND p.date_available <= NOW() AND p2s.store_id = '0' GROUP BY p.product_id ORDER BY p.date_added DESC, LCASE(pd.name) DESC LIMIT 0,4;