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 (
    21343, 21344, 21345, 21346, 21347, 21348, 
    21349, 21350, 21351, 21352, 21353, 
    21354, 21355, 21356, 21357, 21358
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00049

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 (21343,21344,21345,21346,21347,21348,21349,21350,21351,21352,21353,21354,21355,21356,21357,21358) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
21343 Unit Assembly-L.D.C<p>Part number 95300T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21344 Unit assembly-integrated body control module<p>Part number 95400T6111</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21345 Antenna Assembly-Smart Key<p>Part number 95460L1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21346 Antenna Assembly-Smart Key<p>Part number 95460T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21347 FOB-Smart Key<p>Part number 95440T6011</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21348 Unit Assembly - Identity Authentication<p>Part number 95590T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21349 Unit assembly-wireless communication<p>Part number 955B0T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21350 Module assembly - rear curtain<p>Part number 95860T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21351 Module Assembly - Airbag Control<p>Part number 95910T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21352 Cover Assembly - Multi-Sensor<p>Part number 96030T6010DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21353 Cover - Multi-Sensor Blanking<p>Part number 96032T6000DUE</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21354 Unit assembly - mood lamp<p>Part number 92900T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21355 Unit assembly - front radar<p>Part number 99110T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21356 Unit assembly - rear corner radar, left<p>Part number 99140T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21357 Unit assembly - rear corner radar, right<p>Part number 99150T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21358 Unit-Front View Camera<p>Part number 99211T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>