SELECT 
  SQL_CALC_FOUND_ROWS (
    CASE WHEN products.parent_product_id <> 0 THEN products.parent_product_id ELSE products.product_id END
  ) AS product_id, 
  descr1.product as product, 
  companies.company as company_name, 
  MIN(
    IF(
      prices.percentage_discount = 0, 
      prices.price, 
      prices.price - (
        prices.price * prices.percentage_discount
      )/ 100
    )
  ) as price, 
  GROUP_CONCAT(
    products.product_id 
    ORDER BY 
      products.parent_product_id ASC, 
      products.product_id ASC
  ) AS product_ids, 
  GROUP_CONCAT(
    products.product_type 
    ORDER BY 
      products.parent_product_id ASC, 
      products.product_id ASC
  ) AS product_types, 
  GROUP_CONCAT(
    products.parent_product_id 
    ORDER BY 
      products.parent_product_id ASC, 
      products.product_id ASC
  ) AS parent_product_ids, 
  products.product_type, 
  products.parent_product_id, 
  descr1.full_description as full_description 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'en' 
  LEFT JOIN cscart_product_prices as prices ON prices.product_id = products.product_id 
  AND prices.lower_limit = 1 
  LEFT JOIN cscart_product_prices as prices_2 ON prices.product_id = prices_2.product_id 
  AND prices_2.lower_limit = 1 
  AND prices_2.price < prices.price 
  AND prices_2.usergroup_id IN (0, 0, 1) 
  LEFT JOIN cscart_companies AS companies ON companies.company_id = products.company_id 
  INNER JOIN cscart_products_categories as products_categories ON products_categories.product_id = products.product_id 
  INNER JOIN cscart_categories ON cscart_categories.category_id = products_categories.category_id 
  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') 
  AND cscart_categories.storefront_id IN (0, 1) 
WHERE 
  1 
  AND products.product_id NOT IN (21) 
  AND companies.status IN ('A') 
  AND prices.price >= 28.49 
  AND prices.price <= 31.49 
  AND (
    products.usergroup_ids = '' 
    OR FIND_IN_SET(0, products.usergroup_ids) 
    OR FIND_IN_SET(1, products.usergroup_ids)
  ) 
  AND products.status IN ('A') 
  AND prices.usergroup_id IN (0, 0, 1) 
  AND prices_2.price IS NULL 
  AND products.product_type != 'D' 
GROUP BY 
  product_id 
ORDER BY 
  product asc, 
  products.product_id ASC 
LIMIT 
  0, 3

Query time 0.00831

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "51.67"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": true,
        "buffer_result": {
          "using_temporary_table": true,
          "nested_loop": [
            {
              "table": {
                "table_name": "companies",
                "access_type": "ALL",
                "possible_keys": [
                  "PRIMARY"
                ],
                "rows_examined_per_scan": 5,
                "rows_produced_per_join": 1,
                "filtered": "20.00",
                "cost_info": {
                  "read_cost": "3.05",
                  "eval_cost": "0.20",
                  "prefix_cost": "3.25",
                  "data_read_per_join": "6K"
                },
                "used_columns": [
                  "company_id",
                  "status",
                  "company"
                ],
                "attached_condition": "(`atulecarter_atul_demo2`.`companies`.`status` = 'A')"
              }
            },
            {
              "table": {
                "table_name": "cscart_categories",
                "access_type": "ALL",
                "possible_keys": [
                  "PRIMARY",
                  "c_status",
                  "p_category_id"
                ],
                "rows_examined_per_scan": 84,
                "rows_produced_per_join": 3,
                "filtered": "4.00",
                "using_join_buffer": "Block Nested Loop",
                "cost_info": {
                  "read_cost": "19.61",
                  "eval_cost": "0.67",
                  "prefix_cost": "23.53",
                  "data_read_per_join": "8K"
                },
                "used_columns": [
                  "category_id",
                  "storefront_id",
                  "usergroup_ids",
                  "status"
                ],
                "attached_condition": "(((`atulecarter_atul_demo2`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`atulecarter_atul_demo2`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`atulecarter_atul_demo2`.`cscart_categories`.`usergroup_ids`)) and (`atulecarter_atul_demo2`.`cscart_categories`.`status` in ('A','H')) and (`atulecarter_atul_demo2`.`cscart_categories`.`storefront_id` in (0,1)))"
              }
            },
            {
              "table": {
                "table_name": "products_categories",
                "access_type": "ref",
                "possible_keys": [
                  "PRIMARY",
                  "pt"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "category_id"
                ],
                "key_length": "3",
                "ref": [
                  "atulecarter_atul_demo2.cscart_categories.category_id"
                ],
                "rows_examined_per_scan": 4,
                "rows_produced_per_join": 13,
                "filtered": "99.77",
                "using_index": true,
                "cost_info": {
                  "read_cost": "3.64",
                  "eval_cost": "2.68",
                  "prefix_cost": "29.87",
                  "data_read_per_join": "214"
                },
                "used_columns": [
                  "product_id",
                  "category_id"
                ],
                "attached_condition": "(`atulecarter_atul_demo2`.`products_categories`.`product_id` <> 21)"
              }
            },
            {
              "table": {
                "table_name": "products",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY",
                  "status"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "atulecarter_atul_demo2.products_categories.product_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 0,
                "filtered": "7.40",
                "cost_info": {
                  "read_cost": "13.41",
                  "eval_cost": "0.20",
                  "prefix_cost": "45.96",
                  "data_read_per_join": "4K"
                },
                "used_columns": [
                  "product_id",
                  "product_type",
                  "status",
                  "company_id",
                  "usergroup_ids",
                  "parent_product_id"
                ],
                "attached_condition": "((`atulecarter_atul_demo2`.`products`.`company_id` = `atulecarter_atul_demo2`.`companies`.`company_id`) and ((`atulecarter_atul_demo2`.`products`.`usergroup_ids` = '') or find_in_set(0,`atulecarter_atul_demo2`.`products`.`usergroup_ids`) or find_in_set(1,`atulecarter_atul_demo2`.`products`.`usergroup_ids`)) and (`atulecarter_atul_demo2`.`products`.`status` = 'A') and (`atulecarter_atul_demo2`.`products`.`product_type` <> 'D'))"
              }
            },
            {
              "table": {
                "table_name": "prices",
                "access_type": "ref",
                "possible_keys": [
                  "usergroup",
                  "product_id",
                  "lower_limit",
                  "usergroup_id"
                ],
                "key": "usergroup",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "atulecarter_atul_demo2.products_categories.product_id"
                ],
                "rows_examined_per_scan": 4,
                "rows_produced_per_join": 0,
                "filtered": "3.28",
                "index_condition": "((`atulecarter_atul_demo2`.`prices`.`lower_limit` = 1) and (`atulecarter_atul_demo2`.`prices`.`usergroup_id` in (0,0,1)))",
                "cost_info": {
                  "read_cost": "4.20",
                  "eval_cost": "0.03",
                  "prefix_cost": "50.95",
                  "data_read_per_join": "3"
                },
                "used_columns": [
                  "product_id",
                  "price",
                  "percentage_discount",
                  "lower_limit",
                  "usergroup_id"
                ],
                "attached_condition": "((`atulecarter_atul_demo2`.`prices`.`price` >= 28.49) and (`atulecarter_atul_demo2`.`prices`.`price` <= 31.49))"
              }
            },
            {
              "table": {
                "table_name": "prices_2",
                "access_type": "ref",
                "possible_keys": [
                  "usergroup",
                  "product_id",
                  "lower_limit",
                  "usergroup_id"
                ],
                "key": "usergroup",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "atulecarter_atul_demo2.products_categories.product_id"
                ],
                "rows_examined_per_scan": 4,
                "rows_produced_per_join": 0,
                "filtered": "9.83",
                "not_exists": true,
                "cost_info": {
                  "read_cost": "0.55",
                  "eval_cost": "0.01",
                  "prefix_cost": "51.61",
                  "data_read_per_join": "1"
                },
                "used_columns": [
                  "product_id",
                  "price",
                  "lower_limit",
                  "usergroup_id"
                ],
                "attached_condition": "(<if>(found_match(prices_2), isnull(`atulecarter_atul_demo2`.`prices_2`.`price`), true) and <if>(is_not_null_compl(prices_2), ((`atulecarter_atul_demo2`.`prices_2`.`lower_limit` = 1) and (`atulecarter_atul_demo2`.`prices_2`.`price` < `atulecarter_atul_demo2`.`prices`.`price`) and (`atulecarter_atul_demo2`.`prices_2`.`usergroup_id` in (0,0,1))), true))"
              }
            },
            {
              "table": {
                "table_name": "descr1",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY",
                  "product_id"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "product_id",
                  "lang_code"
                ],
                "key_length": "9",
                "ref": [
                  "atulecarter_atul_demo2.products_categories.product_id",
                  "const"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 0,
                "filtered": "100.00",
                "cost_info": {
                  "read_cost": "0.05",
                  "eval_cost": "0.01",
                  "prefix_cost": "51.67",
                  "data_read_per_join": "239"
                },
                "used_columns": [
                  "product_id",
                  "lang_code",
                  "product",
                  "full_description"
                ]
              }
            }
          ]
        }
      }
    }
  }
}