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SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description, 
  cscart_product_descriptions.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    1620, 79, 1619, 1592, 1617, 1616, 1614, 
    1576, 1613, 1612, 1611, 1490, 1610, 
    1609, 1608, 1607, 1606, 1605, 1560, 
    1550, 1548, 1547, 1513, 1604
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00117

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 24,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (1620,79,1619,1592,1617,1616,1614,1576,1613,1612,1611,1490,1610,1609,1608,1607,1606,1605,1560,1550,1548,1547,1513,1604) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id	short_description	full_description	meta_keywords	meta_description	search_words	promo_text	unit_name
79
1490
1513
1547
1548
1550
1560
1576
1592
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1616
1617
1619
1620