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 (
    6945, 6947, 6948, 6959, 6971, 6975, 7019, 
    7060, 7062, 7064, 7065, 7094, 7107, 
    7109, 7122, 7136, 7140, 7158, 7161, 
    7204, 7206, 7209, 7297, 6966, 6846, 
    6873, 6883, 6896, 6907, 6908, 6909, 
    6914, 6927, 6950, 6955, 6956, 6963, 
    7003, 7061, 7104, 7164, 7165, 7179, 
    7181, 7273, 7275, 7305, 7310, 7311, 
    6897, 7106, 6967, 6898, 6901, 6915, 
    6932, 6964, 6969, 7090, 7108, 7201, 
    7203, 7207, 7301, 7312, 6890, 6894, 
    6910, 6919, 6974, 6998, 7114, 7298, 
    7327, 7143, 7309, 7314, 7063
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00159

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "81.91"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 78,
            "rows_produced_per_join": 78,
            "filtered": "100.00",
            "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_products_categories`.`product_id` in (6945,6947,6948,6959,6971,6975,7019,7060,7062,7064,7065,7094,7107,7109,7122,7136,7140,7158,7161,7204,7206,7209,7297,6966,6846,6873,6883,6896,6907,6908,6909,6914,6927,6950,6955,6956,6963,7003,7061,7104,7164,7165,7179,7181,7273,7275,7305,7310,7311,6897,7106,6967,6898,6901,6915,6932,6964,6969,7090,7108,7201,7203,7207,7301,7312,6890,6894,6910,6919,6974,6998,7114,7298,7327,7143,7309,7314,7063))",
            "cost_info": {
              "read_cost": "46.81",
              "eval_cost": "7.80",
              "prefix_cost": "54.61",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "softwarepirmam_hewadelivard_cscart_4.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 3,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "19.50",
              "eval_cost": "0.39",
              "prefix_cost": "81.91",
              "data_read_per_join": "12K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_categories`.`storefront_id` in (0,1)) and ((`softwarepirmam_hewadelivard_cscart_4`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`softwarepirmam_hewadelivard_cscart_4`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`softwarepirmam_hewadelivard_cscart_4`.`cscart_categories`.`usergroup_ids`))) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}