User-474980206 posted
The sample you refer to is accessing a sql database from a web service, not the database calling a web service. It’s not really recommended to call a web service, but the most typical solution is to use a CLR module, google for Sqlserver CLR
web service call.
Your webapi would just be a proxy to the real webapi. You can google for samples as this is common for Ajax calls to be a proxy. You can also configure IIS to be the proxy, with no coding required.