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 (
    89963, 88523, 85722, 85739, 85749, 85759, 
    88193, 88205, 88980, 88997, 88495, 
    85719, 87506, 87522, 88453, 88470, 
    88486, 89837, 89889, 89961, 88522, 
    88986, 88168, 88216
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "10.82"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "8.42",
        "eval_cost": "2.40",
        "prefix_cost": "10.82",
        "data_read_per_join": "91K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (89963,88523,85722,85739,85749,85759,88193,88205,88980,88997,88495,85719,87506,87522,88453,88470,88486,89837,89889,89961,88522,88986,88168,88216)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
85719 Hudson Reed Fluted 600mm Floor Standing 2-Door Unit - Satin White
85722 Hudson Reed Fluted 600mm Floor Standing 2-Door Unit - Satin Anthracite
85739 Hudson Reed Fluted 600mm Floor Standing 2-Door Unit - Satin Grey
85749 Hudson Reed Fluted 600mm Floor Standing 2-Door Unit - Satin Blue
85759 Hudson Reed Fluted 600mm Floor Standing 2-Door Unit - Satin Green
87506 nuie Athena Floor Standing 2 Drawer Vanity Unit 600mm - Anthracite Woodgrain
87522 nuie Athena Floor Standing 2 Drawer Vanity Unit 600mm - Hacienda Black
88168 Hudson Reed Juno 600mm Floor Standing 2-Door Unit - Autumn Oak
88193 Hudson Reed Juno 800mm Floor Standing 2-Door Unit - Graphite Grey
88205 Hudson Reed Juno 800mm Floor Standing 2-Door Unit - Coastal Grey
88216 Juno Components Floor Standing 2 Door Unit (385mm Deep), 600mm - Metallic Slate
88453 nuie Arno 600mm Floor Standing 2-Drawer Unit - Solace Oak
88470 nuie Arno 600mm Floor Standing 2-Drawer Unit - Anthracite
88486 nuie Arno 600mm Floor Standing 2-Drawer Unit - Charcoal Black
88495 nuie Arno 800mm Floor Standing 2-Door Unit - Satin Green
88522 nuie Eden Floor Standing 3 Door 2 Drawer Vanity Cabinet 800mm - Gloss White
88523 nuie Eden Floor Standing 3 Door 2 Drawer Vanity Cabinet 1000mm - Gloss White
88980 Parade Components Floor Standing 2 Door Unit, 600mm - Satin Anthracite
88986 Parade Components Floor Standing 2 Door Unit, 600mm - Gloss White
88997 Parade Components Floor Standing 2 Door Unit, 600mm - Satin Green
89837 Hudson Reed Urban Floor Standing 2 Door 1 Drawer Vanity Unit 500mm - Satin Grey
89889 Hudson Reed Urban Floor Standing 2 Door 1 Drawer Vanity Unit 500mm - Satin Blue
89961 Hudson Reed Urban 500mm Floor Standing 2-Door/Drawer Unit - Satin Green
89963 Hudson Reed Urban 600mm Floor Standing 2-Door/Drawer Unit - Satin Green