Magento – on Magento2.1 how to import product with multiple category

If you want exclude category url from product url for new product you need enable setting from admin>system>catalog>Catalog>Search engine Optimization> Use Categories Path for Product URLsmake itnoalsoCreate Permanent Redirect for URLs if URL Key Changedityes`

Here some other trick

http://www.doingthing.com/blog/item/1164
http://www.mikesmullin.com/development/use-categories-product-urls-magento-seo-without-duplicate-content/

Here the another process of This task...

Step1: create a backup core_url_rewrite table with table data and it structure.

Step2: create another duplicate table of core_url_rewrite using my query below:

CREATE  TABLE  `core_url_rewrite_dump` (  `url_rewrite_id` int( 10  )  unsigned NOT  NULL  AUTO_INCREMENT  COMMENT  'Rewrite Id',
 `store_id` smallint( 5  )  unsigned NOT  NULL DEFAULT  '0' COMMENT  'Store Id',
 `id_path` varchar( 255  )  DEFAULT NULL  COMMENT  'Id Path',
 `request_path` varchar( 255  )  DEFAULT NULL  COMMENT  'Request Path',
 `target_path` varchar( 255  )  DEFAULT NULL  COMMENT  'Target Path',
 `is_system` smallint( 5  ) unsigned DEFAULT  '1' COMMENT  'Defines is Rewrite System',
 `options` varchar( 255  )  DEFAULT NULL  COMMENT  'Options',
 `description` varchar( 255  )  DEFAULT NULL  COMMENT  'Deascription',
 `category_id` int( 10  ) unsigned  DEFAULT NULL  COMMENT  'Category Id',
 `product_id` int( 10  ) unsigned  DEFAULT NULL  COMMENT  'Product Id',
 PRIMARY  KEY (  `url_rewrite_id`  ) ,
 UNIQUE  KEY  `UNQ_CORE_URL_REWRITE_REQUEST_PATH_STORE_ID` (  `request_path` ,  `store_id`  ) ,
 UNIQUE  KEY  `UNQ_CORE_URL_REWRITE_ID_PATH_IS_SYSTEM_STORE_ID` (  `id_path` ,  `is_system` ,  `store_id`  ) ,
 KEY  `IDX_CORE_URL_REWRITE_TARGET_PATH_STORE_ID` (  `target_path` ,  `store_id`  ) ,
 KEY  `IDX_CORE_URL_REWRITE_ID_PATH` (  `id_path`  ) ,
 KEY  `IDX_CORE_URL_REWRITE_STORE_ID` (  `store_id`  ) ,
 KEY  `FK_CORE_URL_REWRITE_CTGR_ID_CAT_CTGR_ENTT_ENTT_ID` (  `category_id`  ) ,
 KEY  `FK_CORE_URL_REWRITE_PRODUCT_ID_CATALOG_CATEGORY_ENTITY_ENTITY_ID` (  `product_id`  )  ) ENGINE  = InnoDB  DEFAULT CHARSET  = utf8 COMMENT  =  'Url Rewrites';

SET SQL_MODE='NO_AUTO_VALUE_ON_ZERO';

INSERT INTO `core_url_rewrite_dump` SELECT * FROM `magento1702v1`.`core_url_rewrite

Step4:

final run the below code

UPDATE `magento1702v1`.`core_url_rewrite` as p  SET `target_path`=(SELECT rurl.request_path
FROM `core_url_rewrite_dump` as rurl
WHERE rurl.product_id IS NOT NULL
AND rurl.category_id IS NULL 
AND rurl.product_id=p.product_id
LIMIT 0 , 1)  
,`options` = 'RP' 
WHERE p. product_id IS NOT NULL
AND p.category_id  IS NOT NULL 

This could be the solution according to Github (Link to Github)

1. Keep the URL key column blank, and make sure you have added the correct category name with upper and lower case letter.

2. Make sure the total length of your categories CSV column is shorter than 255 characters. You can check your url_key length too, but I haven't run into issues with my data set on that one.