From the comments, it looks like your Magento DB does not have a report_compared_product_index table.
Import the following SQL to create this table structure in your database.
CREATE TABLE IF NOT EXISTS `report_compared_product_index` ( `index_id` bigint(20) unsigned NOT NULL COMMENT 'Index Id', `visitor_id` int(10) unsigned DEFAULT NULL COMMENT 'Visitor Id', `customer_id` int(10) unsigned DEFAULT NULL COMMENT 'Customer Id', `product_id` int(10) unsigned NOT NULL COMMENT 'Product Id', `store_id` smallint(5) unsigned DEFAULT NULL COMMENT 'Store Id', `added_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' COMMENT 'Added At' ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='Reports Compared Product Index Table' AUTO_INCREMENT=1 ; ALTER TABLE `report_compared_product_index` ADD PRIMARY KEY (`index_id`), ADD UNIQUE KEY `UNQ_REPORT_COMPARED_PRODUCT_INDEX_VISITOR_ID_PRODUCT_ID` (`visitor_id`,`product_id`), ADD UNIQUE KEY `UNQ_REPORT_COMPARED_PRODUCT_INDEX_CUSTOMER_ID_PRODUCT_ID` (`customer_id`,`product_id`), ADD KEY `IDX_REPORT_COMPARED_PRODUCT_INDEX_STORE_ID` (`store_id`), ADD KEY `IDX_REPORT_COMPARED_PRODUCT_INDEX_ADDED_AT` (`added_at`), ADD KEY `IDX_REPORT_COMPARED_PRODUCT_INDEX_PRODUCT_ID` (`product_id`);
Let me know if this helps.
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