There could be several approaches to your case. Here I will outline one of them. Whether it is the best one, I’m not sure.
First, a Mendix app always requires access to its own dedicated database. It uses this database to store (system) user accounts and other persistent entities.
Ideally, you should consume the data in your MSSQL database via a rest API that “owns” the data; effectively making the data accessible via a well-defined service. I suppose you have considered that architecture.
Since you have asked whether the Mendix app can consume the data from existing MSSQL, yes it can. You can use https://docs.mendix.com/appstore/connectors/database-connector to create bridges into your existing data model. It will be higher maintenance in the long run because Mendix doesn’t manage that database model, therefore you have to do it manually. Also, the initial mapping/querying is a manual task.
Thank your for your reply!
That means it is possible to build an front end without having an appropriate domain model in Mendix?
Does the interface elements in Mendix knows how to deal with SQL commands?