Does the system come with a fully integrated Warehouse Management System (WMS) as part of the ERP software cost?

Nowadays many ERP softwares have integrated WMS system. but the company which uses old version of ERP has to install separate WMS system & in this case it has to link both system databases somehow.[ like what we are using in my company] 

There are many intricacies involved when it comes to integrating WMS with ERP, many companies choose not to integrate due to many practical reasons, Mostly they opt for another system to manage WMS. And it depends on company to company policies. Small to mid range choose not to, where as large corporates will do so. Many ERP systems comes with built in WMS.Some of them sell separately.