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 (
    30896, 30897, 30898, 30899, 30900, 30901, 
    30902, 30903, 30904, 30905, 30906, 
    30907, 30908, 30909, 30910, 30911, 
    30912, 30913, 30914, 30915, 30916, 
    30917, 30918, 30919, 30920, 30921, 
    30922, 30923, 30924, 30925, 30926, 
    30927
  ) 
GROUP BY 
  q_products_categories.product_id

Query time 0.00123

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "133.41"
    },
    "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": 39,
            "rows_produced_per_join": 39,
            "filtered": "100.00",
            "index_condition": "(`portal`.`q_products_categories`.`product_id` in (30896,30897,30898,30899,30900,30901,30902,30903,30904,30905,30906,30907,30908,30909,30910,30911,30912,30913,30914,30915,30916,30917,30918,30919,30920,30921,30922,30923,30924,30925,30926,30927))",
            "cost_info": {
              "read_cost": "78.81",
              "eval_cost": "7.80",
              "prefix_cost": "86.61",
              "data_read_per_join": "624"
            },
            "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": 7,
            "filtered": "20.00",
            "cost_info": {
              "read_cost": "39.00",
              "eval_cost": "1.56",
              "prefix_cost": "133.41",
              "data_read_per_join": "20K"
            },
            "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')))"
          }
        }
      ]
    }
  }
}