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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 (
    11482, 11485, 11516, 13771, 11500, 11498, 
    11522, 11481, 11480, 11525, 11483, 
    11484, 11488, 11491, 11499, 13783, 
    11526, 11523
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 18,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (11482,11485,11516,13771,11500,11498,11522,11481,11480,11525,11483,11484,11488,11491,11499,13783,11526,11523)",
      "attached_condition": "cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id	short_description	full_description
11480		<ul><li>Porcelain tea pot and saucer set with colourful floral decoration</li><li>Dishwasher safe</li><li>Teapot for one in cherry red </li></ul> <p></p>
11481		<ul><li>Porcelain tea pot and saucer set with colourful floral decoration</li><li>Dishwasher safe</li></ul>
11482		<ul><li>Porcelain platter with pink floral prints</li><li>Hand wash only </li></ul>
11483		<ul><li>A beautiful floral porcelain teapot </li><li>Dishwasher and microwave safe</li><li>For hot and cold liquids</li><li>1 l </li></ul>
11484		<p>Porcelain 1Ltr teapot, stainless steel infuser and hand wash recommended.</p>
11485		<ul><li>Porcelain platter with pink floral patterns on a blue background</li><li>Hand wash only</li></ul>
11488		<ul><li>A beautiful floral porcelain teapot </li><li>Dishwasher and microwave safe</li><li>For hot and cold liquids</li><li>1 l </li></ul> <p></p>
11491		<ul><li>Timeless Gin and Tonic cocktail glass </li></ul>
11498		<ul><li>Stainless steel grater with a soft handle</li><li>Premium stainless steel grating surface and frame create a durable and sturdy grating surface as well as an ultra-sharp blade</li></ul>
11499		<ul><li>24cm non stick pan</li><li>It has soft touch handle that allows for easy handling</li><li>Suitable for gas,electric and induction stoves</li></ul>
11500		<ul><li>A rubber wood block for holding knives</li></ul>
11516		<ul><li>Suitable for roasting,comes with carving sets for easy slicing</li><li>Dishwasher and freezer safe</li></ul>
11522		<ul><li>Cocktail Glass</li></ul>
11523		<ul><li>Two wine glasses with a string design</li><li>Box of two </li></ul>
11525		<ul><li>Infuser teapot with bamboo handle</li><li>Borosilicate glass and dishwasher safe</li><li>600ml </li></ul>
11526		<ul><li>Two flute glasses with a string design </li><li>Box of 2 flute glasses</li></ul>
13771
13783