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.storefront_id IN (0, 1) 
  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 (
    13951, 13952, 13953, 13954, 13955, 13956, 
    13957, 13958, 13959, 13960, 13961, 
    13962, 13963, 13964, 13965, 13966, 
    13967, 13968, 13969, 13970, 13971, 
    13972, 13973, 13974, 13975, 13976, 
    13977, 13978, 13979, 13980, 13981, 
    13982, 13983, 13984, 13985, 13986, 
    13987, 13988, 13989, 13990, 13991, 
    13992, 13993, 13994, 13995, 13996, 
    13997, 13998, 13999, 14000, 14001, 
    14002, 14003, 14004, 14005, 14006, 
    14007, 14008, 14009, 14010, 14011, 
    14012, 14013, 14014, 14015, 14016, 
    14017, 14018
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00075

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.176511992,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_products_categories",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "pt"],
          "key": "pt",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "loops": 1,
          "rows": 68,
          "cost": 0.06862106,
          "filtered": 100,
          "attached_condition": "cscart_products_categories.product_id in (13951,13952,13953,13954,13955,13956,13957,13958,13959,13960,13961,13962,13963,13964,13965,13966,13967,13968,13969,13970,13971,13972,13973,13974,13975,13976,13977,13978,13979,13980,13981,13982,13983,13984,13985,13986,13987,13988,13989,13990,13991,13992,13993,13994,13995,13996,13997,13998,13999,14000,14001,14002,14003,14004,14005,14006,14007,14008,14009,14010,14011,14012,14013,14014,14015,14016,14017,14018)",
          "using_index": true
        }
      },
      {
        "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": ["u508912950_dev_2025.cscart_products_categories.category_id"],
          "loops": 68,
          "rows": 1,
          "cost": 0.06409872,
          "filtered": 100,
          "attached_condition": "cscart_categories.storefront_id in (0,1) 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')"
        }
      }
    ]
  }
}