Access SQL Server from smartphone appli

We plan to begin coding (Delphi 10.x) application for smartphone, in a first stage, accessing the customer database, the smartphone being connected to the customer local network.
It seems I have two alternatives : Direct access or REST/HTTPS layer.
Is there some documentation explaining advantages and disavantages of both methods ?
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Sinisa VukSoftware architectCommented:
If you want to use REST - you need to build REST server connected to local database, need to build client app. So, disadvantages are: two apps, more time to build solution, ... but will work with remote/web REST api located anywhere....
Advantage of Direct access (using FireDAC)  - is that you need only client app connected to ex. MS Sql server. But your app will have native sql commands built-in and can be a subject of possible sql injection attack. Direct access will work faster....but it is mainly for local database access.

There are few more solutions too, as answered here...or reviewed here...

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LeTayAuthor Commented:
Many thanks for these very clear explanations
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