SELECT 
  q_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      q_products_categories.link_type = "M", 
      CONCAT(
        q_products_categories.category_id, 
        "M"
      ), 
      q_products_categories.category_id
    )
  ) AS category_ids 
FROM 
  q_products_categories 
  INNER JOIN q_categories ON q_categories.category_id = q_products_categories.category_id 
  AND (
    q_categories.usergroup_ids = '' 
    OR FIND_IN_SET(0, q_categories.usergroup_ids) 
    OR FIND_IN_SET(1, q_categories.usergroup_ids)
  ) 
  AND q_categories.status IN ('A', 'H') 
WHERE 
  q_products_categories.product_id IN (
    40981, 40982, 40983, 40984, 40985, 40986, 
    40987, 40988, 40989, 40990, 40991, 
    40992, 40993, 40994, 40995, 40996, 
    40997, 40998, 40999, 41000, 41001, 
    41002, 41003, 41004, 41005, 41006, 
    41007, 41008, 41009, 41010, 41011, 
    41012
  ) 
GROUP BY 
  q_products_categories.product_id

Query time 0.00138

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "120.41"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "q_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 34,
            "rows_produced_per_join": 34,
            "filtered": "100.00",
            "index_condition": "(`portal`.`q_products_categories`.`product_id` in (40981,40982,40983,40984,40985,40986,40987,40988,40989,40990,40991,40992,40993,40994,40995,40996,40997,40998,40999,41000,41001,41002,41003,41004,41005,41006,41007,41008,41009,41010,41011,41012))",
            "cost_info": {
              "read_cost": "72.81",
              "eval_cost": "6.80",
              "prefix_cost": "79.61",
              "data_read_per_join": "544"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "q_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "portal.q_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 6,
            "filtered": "20.00",
            "cost_info": {
              "read_cost": "34.00",
              "eval_cost": "1.36",
              "prefix_cost": "120.41",
              "data_read_per_join": "17K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "(((`portal`.`q_categories`.`usergroup_ids` = '') or find_in_set(0,`portal`.`q_categories`.`usergroup_ids`) or find_in_set(1,`portal`.`q_categories`.`usergroup_ids`)) and (`portal`.`q_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}