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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 (
    1735, 1602, 1601, 1692, 1696, 1682, 1743, 
    1045, 1046, 1187, 1556, 1555, 1435, 
    1554, 1577, 1194, 1766, 368, 1253, 1553, 
    1371, 1372, 1373, 1374
  ) 
  AND cscart_product_descriptions.lang_code = 'ja'

Query time 0.00109

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 (1735,1602,1601,1692,1696,1682,1743,1045,1046,1187,1556,1555,1435,1554,1577,1194,1766,368,1253,1553,1371,1372,1373,1374) and cscart_product_descriptions.lang_code = 'ja'"
    }
  }
}

Result

product_id	short_description	full_description	meta_keywords	meta_description	search_words	promo_text	unit_name
368
1045
1046
1187
1194
1253
1371
1372
1373
1374
1435
1553
1554
1555
1556
1577
1601
1602
1682
1692
1696
1735
1743
1766