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 (
    51297, 51296, 139, 51300, 51299, 51298, 
    51304, 51303, 51302, 51301, 138, 51443, 
    51309, 51308, 51307, 51306, 51305, 
    129, 51318, 51317, 51316, 51, 51319, 
    51323, 51322, 51321, 51320, 50, 51324, 
    51564, 51568, 51569, 51570, 51571, 
    51572, 51573, 51565, 51574, 51575, 
    51576, 51577, 51566, 51578, 51579, 
    51580, 51581, 51567, 51582, 51583, 
    51584, 51585, 51586
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00210

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "143.41"
    },
    "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": 163,
            "rows_produced_per_join": 163,
            "filtered": "100.00",
            "index_condition": "(`test_uchur_k`.`cscart_products_categories`.`product_id` in (51297,51296,139,51300,51299,51298,51304,51303,51302,51301,138,51443,51309,51308,51307,51306,51305,129,51318,51317,51316,51,51319,51323,51322,51321,51320,50,51324,51564,51568,51569,51570,51571,51572,51573,51565,51574,51575,51576,51577,51566,51578,51579,51580,51581,51567,51582,51583,51584,51585,51586))",
            "cost_info": {
              "read_cost": "70.06",
              "eval_cost": "16.30",
              "prefix_cost": "86.36",
              "data_read_per_join": "2K"
            },
            "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": [
              "test_uchur_k.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 8,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "40.75",
              "eval_cost": "0.82",
              "prefix_cost": "143.41",
              "data_read_per_join": "43K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`test_uchur_k`.`cscart_categories`.`storefront_id` in (0,1)) and ((`test_uchur_k`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`test_uchur_k`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`test_uchur_k`.`cscart_categories`.`usergroup_ids`))) and (`test_uchur_k`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}