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.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    21213, 21214, 21215, 21216, 21217, 21218, 
    21219, 21220, 21221, 21222, 21223, 
    21224, 21225, 21226, 21227, 21228
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (21213,21214,21215,21216,21217,21218,21219,21220,21221,21222,21223,21224,21225,21226,21227,21228) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
21213 Adjuster Assembly-Height<p>Part number 88890G3000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21214 Seat belt assembly-rear left<p>Part number 89870T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21215 Seat belt assembly-rear right<p>Part number 89880T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21216 Seat Belt Assembly - Rear Center<p>Part number 89850T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21217 2nd row seat buckle left<p>Part number 89830T6200DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21218 Right side of 2nd row seat buckle<p>Part number 89840T6200DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21219 Buckle Assembly - Center Seat Belt<p>Part number 89860T6100DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21220 3rd row seat buckle, left<p>Part number 89833T6100DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21221 3rd row seat buckle, right<p>Part number 89843T6100DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21222 Seat belt assembly - 3rd row left<p>Part number 89813T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21223 Seat belt assembly - 3rd row right<p>Part number 89823T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21224 Wiring Assembly-Main<p>Part number 91105T6742</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21225 Junction box assembly - instrument panel<p>Part number 91950T6022</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21226 Bracket-wiring mounting<p>Part number 91931T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21227 Bracket-instrument panel junction box<p>Part number 919G5T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21228 Protector-wiring<p>Part number 91961T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>