MySQL Error Occurred

Error Message:
1021: Disk full (/var/mysqltmp/#sql_614e_21.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")

SQL:
SELECT cubecart_cats_idx.cat_id, cubecart_cats_idx.productId, productCode, quantity, description, image, price, name, popularity, sale_price, stock_level, useStockLevel FROM cubecart_cats_idx INNER JOIN cubecart_inventory ON cubecart_cats_idx.productId = cubecart_inventory.productId WHERE cubecart_cats_idx.cat_id = '0' AND cubecart_inventory.status = 0 GROUP BY cubecart_inventory.productId