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SELECT 
  cscart_ult_product_descriptions.product_id, 
  cscart_ult_product_descriptions.short_description, 
  IF(
    cscart_ult_product_descriptions.short_description = "", 
    cscart_ult_product_descriptions.full_description, 
    ""
  ) AS full_description, 
  cscart_ult_product_descriptions.meta_keywords, 
  cscart_ult_product_descriptions.meta_description, 
  cscart_ult_product_descriptions.search_words, 
  cscart_ult_product_descriptions.promo_text 
FROM 
  cscart_ult_product_descriptions 
WHERE 
  cscart_ult_product_descriptions.product_id IN (
    42487, 42577, 42576, 42575, 42574, 42573, 
    42572, 42478, 42787, 42817, 42638, 
    42589, 42493, 42492, 42491, 42630, 
    42629, 42518, 42568, 42422
  ) 
  AND cscart_ult_product_descriptions.company_id = 1 
  AND cscart_ult_product_descriptions.lang_code = 'en'

Query time 0.00018

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	cscart_ult_product_descriptions	ALL	PRIMARY,product_id,company_id				1	Using where