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SELECT 
  SQL_CALC_FOUND_ROWS products.product_id, 
  IF(
    shared_descr.product_id IS NOT NULL, 
    shared_descr.product, descr1.product
  ) as product, 
  companies.company as company_name, 
  products.product_type, 
  products.parent_product_id, 
  products.free_shipping, 
  products.product_label_id, 
  products.product_label_id_by_admin, 
  categories.id_path 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'en' 
  LEFT JOIN cscart_product_prices as prices ON prices.product_id = products.product_id 
  AND prices.lower_limit = 1 
  LEFT JOIN cscart_companies AS companies ON companies.company_id = products.company_id 
  INNER JOIN cscart_products_categories as products_categories ON products_categories.product_id = products.product_id 
  INNER JOIN cscart_categories ON cscart_categories.category_id = products_categories.category_id 
  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') 
  AND cscart_categories.storefront_id IN (0, 1) 
  LEFT JOIN cscart_ult_product_descriptions shared_descr ON shared_descr.product_id = products.product_id 
  AND shared_descr.company_id = 1 
  AND shared_descr.lang_code = 'en' 
  LEFT JOIN cscart_categories as categories ON categories.category_id = products_categories.category_id 
  LEFT JOIN cscart_product_label as product_label ON product_label.id = products.product_label_id_by_admin 
WHERE 
  1 
  AND cscart_categories.category_id IN (
    166, 165, 167, 168, 169, 170, 171, 172, 
    174, 175, 176, 177, 178, 179, 180, 181, 
    182, 199, 185, 186, 187, 188, 189, 190, 
    191, 194, 193, 195, 196, 197, 198, 200, 
    201, 202, 234, 235, 236, 237, 238, 240, 
    254, 255, 263
  ) 
  AND products.product_id NOT IN (320) 
  AND companies.status IN ('A') 
  AND products.amount > 0 
  AND (
    products.usergroup_ids = '' 
    OR FIND_IN_SET(0, products.usergroup_ids) 
    OR FIND_IN_SET(1, products.usergroup_ids)
  ) 
  AND products.status IN ('A') 
  AND prices.usergroup_id IN (0, 0, 1) 
  AND products.parent_product_id = 0 
GROUP BY 
  products.product_id 
ORDER BY 
  product asc, 
  products.product_id ASC 
LIMIT 
  0, 4

Query time 0.00527

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	companies	system	PRIMARY				1	Using temporary; Using filesort
1	SIMPLE	cscart_categories	ALL	PRIMARY,c_status,p_category_id				83	Using where
1	SIMPLE	products_categories	range	PRIMARY,pt	PRIMARY	6		206	Using where; Using index; Using join buffer (flat, BNL join)
1	SIMPLE	prices	ref	usergroup,product_id,lower_limit,usergroup_id	usergroup	3	cscart_dev_4_16.products_categories.product_id	1	Using where; Using index
1	SIMPLE	products	eq_ref	PRIMARY,status,idx_parent_product_id	PRIMARY	3	cscart_dev_4_16.products_categories.product_id	1	Using where
1	SIMPLE	shared_descr	eq_ref	PRIMARY,product_id,company_id	PRIMARY	13	cscart_dev_4_16.products_categories.product_id,const,const	1	Using where
1	SIMPLE	categories	eq_ref	PRIMARY,p_category_id	PRIMARY	3	cscart_dev_4_16.cscart_categories.category_id	1
1	SIMPLE	descr1	eq_ref	PRIMARY,product_id	PRIMARY	9	cscart_dev_4_16.products_categories.product_id,const	1	Using where

Result

product_id	product	company_name	product_type	free_shipping	id_path
148	16GB A Series Walkman Video MP3	CS-Cart	P	N	166/177/179
180	18-55mm Portrait Lens	CS-Cart	P	N	166/196/200
18	3D Blu-ray Disc™ Player (BD-D7000)	CS-Cart	P	N	166/174/194
16	3D Blu-ray Disc™ Player (BD-D7500)	CS-Cart	P	N	166/174/194