SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
WHERE 
  cscart_products_categories.product_id IN (
    278, 280, 282, 247, 248, 241, 244, 245, 
    246, 240, 6, 66, 166, 214, 219, 221, 223, 
    192, 194, 195, 196, 197, 198, 199, 200, 
    201, 202, 203, 204, 205, 206, 207, 208, 
    209, 210, 211, 212, 213, 215, 217, 218, 
    220, 222, 224, 225, 226, 227, 228, 229, 
    230, 231, 232, 233, 234, 235, 236, 237, 
    238, 239, 242, 243, 78, 79, 80, 81, 82, 
    83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 
    93, 94, 95, 96, 97, 100, 101, 102, 103, 
    104, 105, 106, 107, 108, 109, 110, 111, 
    112, 113, 114
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00096

JSON explain

{
  "query_block": {
    "select_id": 1,
    "read_sorted_file": {
      "filesort": {
        "sort_key": "cscart_products_categories.product_id",
        "table": {
          "table_name": "cscart_products_categories",
          "access_type": "ALL",
          "possible_keys": ["PRIMARY", "pt"],
          "rows": 267,
          "filtered": 37.07865143,
          "attached_condition": "cscart_products_categories.product_id in (278,280,282,247,248,241,244,245,246,240,6,66,166,214,219,221,223,192,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,215,217,218,220,222,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,242,243,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114)"
        }
      }
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "c_status", "p_category_id"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "ref": ["smscrm_edev.cscart_products_categories.category_id"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "(cscart_categories.usergroup_ids = '' or find_in_set(0,cscart_categories.usergroup_ids) or find_in_set(1,cscart_categories.usergroup_ids)) and cscart_categories.`status` in ('A','H')"
    }
  }
}