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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    276544, 276545, 276546, 276547, 276548, 
    276549, 276550, 276551, 276552, 276553, 
    276572, 276573, 276574, 276575, 276588, 
    276589, 276590, 276591, 276592, 276593
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "44.01"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 20,
      "rows_produced_per_join": 20,
      "filtered": "100.00",
      "index_condition": "((`s2cart`.`cscart_product_descriptions`.`product_id` in (276544,276545,276546,276547,276548,276549,276550,276551,276552,276553,276572,276573,276574,276575,276588,276589,276590,276591,276592,276593)) and (`s2cart`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "42.01",
        "eval_cost": "2.00",
        "prefix_cost": "44.01",
        "data_read_per_join": "151K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ]
    }
  }
}

Result

product_id short_description full_description
276544 Miniature Circuit Breaker - S200M - 4P - C
276545 Miniature Circuit Breaker - S200M - 4P - C
276546 Miniature Circuit Breaker - S200M - 4P - D
276547 Miniature Circuit Breaker - S200M - 4P - C
276548 Miniature Circuit Breaker - S200M - 4P - D
276549 Miniature Circuit Breaker - S200M - 4P - C
276550 Miniature Circuit Breaker - S200M - 4P - D
276551 Miniature Circuit Breaker - S200M - 4P - C
276552 Miniature Circuit Breaker - S200M - 4P - D
276553 Miniature Circuit Breaker - S200M - 4P - C
276572 Miniature Circuit Breaker - S200M - 4P - D
276573 Miniature Circuit Breaker - S200M - 4P - C
276574 Miniature Circuit Breaker - S200M - 4P - D
276575 Miniature Circuit Breaker - S200M - 4P - C
276588 Miniature Circuit Breaker - SH200M - 1P - C
276589 Miniature Circuit Breaker - SH200M - 1P - C
276590 Miniature Circuit Breaker - SH200M - 1P - C
276591 Miniature Circuit Breaker - SH200M - 1P - C
276592 Miniature Circuit Breaker - SH200M - 1P - C
276593 Miniature Circuit Breaker - SH200M - 1P - C