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, 
  product_position_source.position AS position 
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') 
  LEFT JOIN q_products_categories AS product_position_source ON q_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 168 
WHERE 
  q_products_categories.product_id IN (
    29282, 29283, 29314, 29341, 29690, 29694, 
    29702, 29799, 30319, 30339, 30770, 
    30781, 30782, 30783, 30787, 30794, 
    30799, 30815, 30860, 30873, 30876, 
    30899, 30911, 30920, 30931, 30937, 
    30939, 30943, 30957, 30972, 31015, 
    31045
  ) 
GROUP BY 
  q_products_categories.product_id

Query time 0.00096

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "168.81"
    },
    "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": 36,
            "rows_produced_per_join": 36,
            "filtered": "100.00",
            "index_condition": "(`portal`.`q_products_categories`.`product_id` in (29282,29283,29314,29341,29690,29694,29702,29799,30319,30339,30770,30781,30782,30783,30787,30794,30799,30815,30860,30873,30876,30899,30911,30920,30931,30937,30939,30943,30957,30972,31015,31045))",
            "cost_info": {
              "read_cost": "75.21",
              "eval_cost": "7.20",
              "prefix_cost": "82.41",
              "data_read_per_join": "576"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "portal.q_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 36,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "36.00",
              "eval_cost": "7.20",
              "prefix_cost": "125.61",
              "data_read_per_join": "576"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "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": "36.00",
              "eval_cost": "1.44",
              "prefix_cost": "168.81",
              "data_read_per_join": "19K"
            },
            "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')))"
          }
        }
      ]
    }
  }
}