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SELECT 
  cscart_categories.*, 
  cscart_category_descriptions.*, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path 
FROM 
  cscart_categories 
  LEFT JOIN cscart_category_descriptions ON cscart_category_descriptions.category_id = cscart_categories.category_id 
  AND cscart_category_descriptions.lang_code = 'fr' 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = 841 
  AND cscart_seo_names.type = 'c' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'fr' 
  AND cscart_seo_names.company_id = cscart_categories.company_id 
WHERE 
  cscart_categories.category_id = 841 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.company_id = 3

Query time 0.00040

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows
1	SIMPLE	cscart_categories	const	PRIMARY,c_status,p_category_id,idx_category_id	PRIMARY	3	const	1
1	SIMPLE	cscart_category_descriptions	const	PRIMARY	PRIMARY	9	const,const	1
1	SIMPLE	cscart_seo_names	const	PRIMARY,dispatch	PRIMARY	210	const,const,const,const,const	1

Result

category_id	parent_id	id_path	level	company_id	usergroup_ids	status	product_count	position	timestamp	size_chart_id	is_op	localization	age_verification	age_limit	parent_age_verification	parent_age_limit	selected_views	default_view	product_details_view	product_columns	is_trash	staff_notes	action	lang_code	category	description	meta_keywords	meta_description	page_title	age_warning_message	custom_header	seo_name	seo_path
841	834	741/834/841	3	3	0	A	24	10	1457823600	0	N		N	0	N	0			default	0	N			fr	Escaliers escamotables	<p><iframe allowfullscreen="" frameborder="0" height="360" src="https://www.youtube.com/embed/UZid2acUowU?feature=player_detailpage" width="640"></iframe></p>	FAKRO Escalier escamotable LWS Plus, avec une echelle en bois ; FAKRO Escalier escamotable LWK Plus, avec une echelle en bois ; FAKRO Escalier escamotable LTK Energy, avec une echelle en bois, super thermo-isolant ; une echelle en metallique ;	l’escalier escamotable en bois de pin ; Embouts de protection de sol ; Trappe blanche ; Joint périphérique ; Main courante ; destiné aux bâtiments avec une importante différence de températures entre la pièce habitable au grenier ;				fakro-escaliers-escamotables	741/834