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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 (11777, 888, 3415, 13049) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00019

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": 4,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (11777,888,3415,13049)",
      "attached_condition": "cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id	short_description	full_description
888		<ul style="padding:0px;color:#686868;font-family:sourcesanspro, Helvetica, Tahoma, Geneva, Arial, sans-serif;font-size:16px;"><li>HTH Floater+ (Pool Chlorine)</li><li>Contains: slow-release chlorine (stabilised)</li> <li>Shock treatment</li> <li>Algaecide</li> <li>Clarifier</li> <li>See-through so you know when it is empty</li> <li>1.6kg treats up to 70 000L</li> <li>750g treats up to 30 000L</li> </ul>
3415		<ul><li>The Squirt PS4 will make you wonder how you ever managed without it</li><li>With pliers, scissors and a pocketful of other features, this lightweight mini-tool comes in handy for everything from snipping fishing line to wrapping a birthday present on the go</li><li><b>Spring-action Needlenose Pliers</b></li><li>Use one hand to hold small objects or access narrow spaces</li><li><b>Spring-action Regular Pliers</b></li><li>Easily hold and manipulate materials with this one-handed tool</li><li><b>Spring-action Wire Cutters</b></li><li>Easily cut through regular-gauge wires with this one-handed tool</li><li><b>420HC Knife</b></li><li>A knife crafted from 420HC, a high-carbon stainless steel that is corrosion resistant and can be easily maintained.</li><li><b>Spring-action Scissors</b></li><li>Use one hand to quickly and easily cut through thin materials</li><li><b>Flat/Phillips Screwdriver</b></li><li>Tighten and loosen flat or Phillips head screws</li><li><b>Bottle Opener</b></li><li>A tool that allows the user to pop the top on a favourite beverage</li><li><b>Wood/Metal File</b></li><li>Precisely file and smooth edges on wood and metal surfaces</li><li><b>Medium Screwdriver</b></li><li>Tighten and loosen medium-size flathead screws</li><li><b>Key Ring Attachment</b></li><li>A split ring loop for attaching a tool to a key ring, allowing the user to keep their multi-tool handy at all times</li><li><b>Outside-accessible Features</b></li><li>This multi-tool features tools that are accessible while the tool is in its folded or closed position, mimicking the functionality of a pocket knife.</li></ul> <p><br /></p> <p></p>
11777	<p>Please note This KIT is available on order the ETA will be 3-4 working days from date of purchase.</p>
13049