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 (
    20733, 20734, 20735, 20736, 20737, 20738, 
    20739, 20740, 20741, 20742, 20743, 
    20744, 20745, 20746, 20747, 20748
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00107

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 (20733,20734,20735,20736,20737,20738,20739,20740,20741,20742,20743,20744,20745,20746,20747,20748) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description unit_name
20733 Trim assembly - luggage side, right<p>Part number 85740T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20734 Tray assembly-luggage, center<p>Part number 85750T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20735 Cover-lamp service, left<p>Part number 85734T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20736 Cover-lamp service, right<p>Part number 85744T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20737 Trim assembly - rear transverse<p>Part number 85770T1000NNB</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20738 Trim Assembly - Front Pillar<p>Part number 85810T1600NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20739 Trim assembly - front pillar, right<p>Part number 85820T1600NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20740 Trim Assembly - Cowl Side Left<p>Part number 85823T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20741 Trim Assembly - Cowl Side Right<p>Part number 85824T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20742 Trim assembly - center pillar upper, left<p>Part number 85830T1600NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20743 Trim assembly - center pillar upper, right<p>Part number 85840T1600NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20744 Knob-Height Adjust, Left<p>Part number 85834T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20745 Cover assembly-height adjust, left<p>Part number 85833T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20746 Knob-Height Adjust, Right<p>Part number 85844T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20747 Trim assembly - center pillar lower, left<p>Part number 85835T1500NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
20748 Cover assembly-height adjust, right<p>Part number 85843T1000NBD</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>