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SELECT 
  jmj_attachments.*, 
  jmj_attachment_descriptions.description 
FROM 
  jmj_attachments 
  LEFT JOIN jmj_attachment_descriptions ON jmj_attachments.attachment_id = jmj_attachment_descriptions.attachment_id 
  AND lang_code = 'en' 
WHERE 
  object_type = 'product' 
  AND object_id = 821 
  AND type = 'M' 
  AND (
    usergroup_ids = '' 
    OR FIND_IN_SET(0, usergroup_ids) 
    OR FIND_IN_SET(1, usergroup_ids)
  ) 
  AND status = 'A' 
ORDER BY 
  position

Query time 0.01119

JSON explain

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