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 (
    6780, 6689, 6769, 6686, 6688, 6785, 6690, 
    6670, 6799, 6687, 6773, 6795, 6777, 
    6784, 6691, 6807, 6770, 6781, 6783, 
    6776, 6797, 6774, 6790, 7315, 6746, 
    6808, 6731, 6792, 6732, 6744, 6756, 
    6782, 6673, 6714, 6789, 6796, 6694, 
    6778, 6793, 6674, 6718, 6816, 6775, 
    6809, 6715, 6758, 6766, 6768, 6717, 
    6771, 6813, 6716, 6772, 6669, 6671, 
    6812, 6761, 6672, 6760, 6767, 6815, 
    6759, 6668, 6762, 6765, 6810, 6757, 
    6764, 6811, 6763, 6814
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00266

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "107.36"
    },
    "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": 112,
            "rows_produced_per_join": 112,
            "filtered": "100.00",
            "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_products_categories`.`product_id` in (6780,6689,6769,6686,6688,6785,6690,6670,6799,6687,6773,6795,6777,6784,6691,6807,6770,6781,6783,6776,6797,6774,6790,7315,6746,6808,6731,6792,6732,6744,6756,6782,6673,6714,6789,6796,6694,6778,6793,6674,6718,6816,6775,6809,6715,6758,6766,6768,6717,6771,6813,6716,6772,6669,6671,6812,6761,6672,6760,6767,6815,6759,6668,6762,6765,6810,6757,6764,6811,6763,6814))",
            "cost_info": {
              "read_cost": "56.96",
              "eval_cost": "11.20",
              "prefix_cost": "68.16",
              "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": 5,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "28.00",
              "eval_cost": "0.56",
              "prefix_cost": "107.36",
              "data_read_per_join": "17K"
            },
            "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')))"
          }
        }
      ]
    }
  }
}