There is an undocumented API on the Salesforce Sales Cloud connector that lets you pass an SOQL query directly to Salesforce. OCNQL (Open Connectors Query Language) supports, for the most part, the most basic functionality of SQL. Typically something like this:
select * from Account where Name = 'TestAccount'
Salesforce actually supports much more than this. Such as aggregate functions like count(Id) and even INNER JOIN and OUTER JOIN.
See this documentation for what salesforce supports: https://developer.salesforce.com/docs/atlas.en-us.soql_sosl.meta/soql_sosl/sforce_api_calls_soql.htm
On SAP Cloud Platform Open Connectors, you can use this extra querying functionality through the GET /query api.
The syntax is as follows:
GET /query?q=SELECT count(Id) FROM Contact WHERE name = 'test'&page=1&pageSize=200
GET /query?q=SELECT Amount, Id, Name, (SELECT Quantity, ListPrice, PricebookEntry.UnitPrice, PricebookEntry.Name FROM OpportunityLineItems) FROM Opportunity
This API is undocumented because, you will not be able to easily use a transformation on the data that comes back, and this api will not be standardized to the hub. In other words, this will only ever work for Salesforce.