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SELECT 
  cscart_products.product_id, 
  cscart_products.company_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = 'M', 
      CONCAT(
        cscart_products_categories.category_id, 
        'M'
      ), 
      cscart_products_categories.category_id
    )
  ) as category_ids, 
  cscart_products.product_code, 
  cscart_products.weight, 
  cscart_products.tracking, 
  cscart_product_descriptions.product, 
  cscart_product_descriptions.short_description, 
  cscart_products.is_edp, 
  cscart_products.edp_shipping, 
  cscart_products.shipping_freight, 
  cscart_products.free_shipping, 
  cscart_products.zero_price_action, 
  cscart_products.tax_ids, 
  cscart_products.qty_step, 
  cscart_products.list_qty_count, 
  cscart_products.max_qty, 
  cscart_products.min_qty, 
  cscart_products.amount as in_stock, 
  cscart_products.shipping_params, 
  cscart_companies.status as company_status, 
  cscart_products.out_of_stock_actions, 
  cscart_products.updated_timestamp, 
  cscart_company_descriptions.i18n_company as company_name 
FROM 
  cscart_products 
  LEFT JOIN cscart_product_descriptions ON cscart_product_descriptions.product_id = cscart_products.product_id 
  AND cscart_product_descriptions.lang_code = 'fr' 
  INNER JOIN cscart_products_categories ON cscart_products_categories.product_id = cscart_products.product_id 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  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_products.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_products.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_products.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  AND cscart_products.status IN ('A', 'H') 
  LEFT JOIN cscart_companies ON cscart_companies.company_id = cscart_products.company_id 
  LEFT JOIN cscart_company_descriptions ON cscart_company_descriptions.company_id = cscart_products.company_id 
  AND cscart_company_descriptions.lang_code = 'fr' 
WHERE 
  cscart_products.product_id = 625 
GROUP BY 
  cscart_products.product_id

Query time 0.00048

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "const",
      "possible_keys": ["PRIMARY", "status"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_companies",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "4",
      "used_key_parts": ["company_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_company_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "10",
      "used_key_parts": ["company_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_products_categories",
      "access_type": "ref",
      "possible_keys": ["PRIMARY", "pt"],
      "key": "pt",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100,
      "using_index": true
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "c_status", "p_category_id"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "ref": ["multi_vendor.cscart_products_categories.category_id"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "cscart_categories.storefront_id in (0,1) 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.`status` in ('A','H')"
    }
  }
}

Result

product_id	company_id	category_ids	product_code	weight	tracking	product	short_description	is_edp	edp_shipping	shipping_freight	free_shipping	zero_price_action	tax_ids	qty_step	list_qty_count	max_qty	min_qty	in_stock	shipping_params	company_status	out_of_stock_actions	updated_timestamp	company_name
625	3	199M	B00F3IUN24	0.000		Provisoire Résine Fixe - G3		N	N	0.00	N							100000	a:5:{s:16:"min_items_in_box";i:0;s:16:"max_items_in_box";i:0;s:10:"box_length";i:0;s:9:"box_width";i:0;s:10:"box_height";i:0;}	A	N	1767480454	Laboratoire Dental Cortex - Paris - France - Depuis 1986