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 = 12 
WHERE 
  q_products_categories.product_id IN (
    32749, 32750, 32751, 32752, 32753, 32754, 
    32755, 32756, 32757, 32758, 32759, 
    32760, 32761, 32762, 32763, 32764, 
    32765, 32766, 32767, 32768, 32769, 
    32770, 32771, 32772, 32773, 32774, 
    32775, 32776, 32777, 32778, 32779, 
    32780
  ) 
GROUP BY 
  q_products_categories.product_id

Query time 0.00082

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "180.21"
    },
    "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 (32749,32750,32751,32752,32753,32754,32755,32756,32757,32758,32759,32760,32761,32762,32763,32764,32765,32766,32767,32768,32769,32770,32771,32772,32773,32774,32775,32776,32777,32778,32779,32780))",
            "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": "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": 39,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "39.00",
              "eval_cost": "7.80",
              "prefix_cost": "133.41",
              "data_read_per_join": "624"
            },
            "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": "39.00",
              "eval_cost": "1.56",
              "prefix_cost": "180.21",
              "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')))"
          }
        }
      ]
    }
  }
}