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 (
    32785, 32786, 32787, 32788, 32789, 32790, 
    32791, 32792, 32793, 32794, 32795, 
    32796, 32797, 32798, 32799, 32800, 
    32801, 32802, 32803, 32804, 32805, 
    32806, 32807, 32808, 32809, 32810, 
    32811, 32812, 32813, 32814, 32815, 
    32816
  ) 
GROUP BY 
  q_products_categories.product_id

Query time 0.00084

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "172.41"
    },
    "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": 54,
            "rows_produced_per_join": 54,
            "filtered": "100.00",
            "index_condition": "(`portal`.`q_products_categories`.`product_id` in (32785,32786,32787,32788,32789,32790,32791,32792,32793,32794,32795,32796,32797,32798,32799,32800,32801,32802,32803,32804,32805,32806,32807,32808,32809,32810,32811,32812,32813,32814,32815,32816))",
            "cost_info": {
              "read_cost": "96.81",
              "eval_cost": "10.80",
              "prefix_cost": "107.61",
              "data_read_per_join": "864"
            },
            "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": 10,
            "filtered": "20.00",
            "cost_info": {
              "read_cost": "54.00",
              "eval_cost": "2.16",
              "prefix_cost": "172.41",
              "data_read_per_join": "28K"
            },
            "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')))"
          }
        }
      ]
    }
  }
}