Doc improvement for database tracer (#11)

Author: arminru

README.md

@@ -285,6 +285,8 @@ See the documentation for more information:
 * [`trace_sql_database_request`](https://dynatrace.github.io/OneAgent-SDK-for-Python/docs/sdkref.html#oneagent.sdk.SDK.trace_sql_database_request)
 * [`DatabaseRequestTracer`](https://dynatrace.github.io/OneAgent-SDK-for-Python/docs/sdkref.html#oneagent.sdk.tracers.DatabaseRequestTracer)
 
+Please note that SQL database traces are only created if they occur within some other SDK trace (e.g. incoming remote call).
+
 <a name="incoming-web-requests"></a>
 ### Incoming web requests
 

src/oneagent/sdk/__init__.py

@@ -136,6 +136,10 @@ def create_web_application_info(
     def trace_sql_database_request(self, database, sql):
         '''Create a tracer for the given database info and SQL statement.
 
+        .. note::
+            Please note that SQL database traces are only created if they occur
+            within some other SDK trace (e.g. incoming remote call).
+
         :param DbInfoHandle database: Database information (see
             :meth:`create_database_info`).
         :param str sql: The SQL statement to trace.