Error: Expression #5 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'autolubr_site.ui.filename' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
Trace on: /var/www/vhosts/autolubricants.ro/httpdocs/include/class/db.class.php(339)

SQL: SELECT
`produse`.id, `produse`.nume,
`produse`.pret, `produse`.pret_nou,
IF(
ISNULL(ui.parent_id),
'template/images/default.jpg',
CONCAT('userfiles/', ui.category, '/', ui.parent_id, '/', ui.filename)
) AS pic
FROM `produse`
LEFT JOIN `sys_upload_images` ui ON(ui.parent_id=produse.id AND ui.category='produse')
JOIN `sys_select_ref` sr ON(
sr.category='produse' AND
sr.category_field='recomandate' AND
sr.ref_id=produse.id
)
WHERE sr.category_id='31'
GROUP BY produse.id
LIMIT 3