We have some databases and tables on SQL 2017, we want to show one table content on SharePoint, is it possible?
Yes, it's possible. You could use Business Connectivity Services to access the data in SharePoint via external lists. External lists allow you to manage external SQL data using the SharePoint user interface.
Alternatively, you could create a bespoke application which returns the data via an API. Once you have that API, you can then create an SPFx web part that displays the data via the API.
To provide an idea: If you use Power BI, connect it to the database and display the table through Power BI. Then you could easily display the report in SharePoint using the Power BI web part.
By the way, Power BI needs to access the database through an on-premises data gateway.
Reference for Power BI to connect to SQL server: Refresh data from an on-premises SQL Server database
Reference for using Power BI Web Parts in SharePoint: Embed a report web part in SharePoint Online
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