Why I'm getting this error mysqli::query(): (21000/1242):

HI,

My website is now working properly all warning are showing on the page and even I got error in log ...

2016-04-19 6:29:36 - PHP Warning: mysqli::query(): (21000/1242): Subquery returns more than 1 row in /home/ladycsj6/public_html/system/library/db/mysqli.php on line 19
2016-04-19 6:29:36 - PHP Notice: Error: Subquery returns more than 1 row<br />Error No: 1242<br />SELECT DISTINCT *, pd.name AS name, p.image, m.name AS manufacturer, (SELECT price FROM 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 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, (SELECT points FROM product_reward pr WHERE pr.product_id = p.product_id AND customer_group_id = '1') AS reward, (SELECT ss.name FROM stock_status ss WHERE ss.stock_status_id = p.stock_status_id AND ss.language_id = '1') AS stock_status, (SELECT wcd.unit FROM weight_class_description wcd WHERE p.weight_class_id = wcd.weight_class_id AND wcd.language_id = '1') AS weight_class, (SELECT lcd.unit FROM length_class_description lcd WHERE p.length_class_id = lcd.length_class_id AND lcd.language_id = '1') AS length_class, (SELECT AVG(rating) AS total FROM review r1 WHERE r1.product_id = p.product_id AND r1.status = '1' GROUP BY r1.product_id) AS rating, (SELECT COUNT(*) AS total FROM review r2 WHERE r2.product_id = p.product_id AND r2.status = '1' GROUP BY r2.product_id) AS reviews, p.sort_order FROM product p LEFT JOIN product_description pd ON (p.product_id = pd.product_id) LEFT JOIN product_to_store p2s ON (p.product_id = p2s.product_id) LEFT JOIN manufacturer m ON (p.manufacturer_id = m.manufacturer_id) WHERE p.product_id = '978' AND pd.language_id = '1' AND p.status = '1' AND p.date_available <= NOW() AND p2s.store_id = '0' in /home/ladycsj6/public_html/system/library/db/mysqli.php on line 41
2016-04-19 6:29:36 - PHP Notice: Trying to get property of non-object in /home/ladycsj6/public_html/catalog/model/catalog/product.php on line 10



Please help me.. How to fix this issue.

Done.. rewards was duplicated .. Now deleted from PHP DB rewards.

i got this message , after i want to edit or add new product . would you please help me . thanks ...
Warning: mysqli::query(): (21000/1242): Subquery returns more than 1 row in /home3/guprojec/public_html/unipartsbg/system/storage/modification/system/library/db/mysqli.php on line 25

Well its seems to be the rewards table ive just fixed mine, use phpadmin to view db look in oc_products_rewards table and look for duplicate product_id's