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SELECT 
  csscart_product_files.*, 
  csscart_product_file_descriptions.file_name, 
  csscart_product_file_descriptions.license, 
  csscart_product_file_descriptions.readme 
FROM 
  csscart_product_files 
  LEFT JOIN csscart_product_file_descriptions ON csscart_product_file_descriptions.file_id = csscart_product_files.file_id 
  AND csscart_product_file_descriptions.lang_code = 'en' 
WHERE 
  1 = 1 
  AND csscart_product_files.product_id = 245 
  AND preview_path != '' 
  AND csscart_product_files.status = 'A' 
ORDER BY 
  csscart_product_files.position asc, 
  csscart_product_file_descriptions.file_name asc

Query time 0.00130

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}