the information you're requesting is not exposed via API as it's really just internal, but you can find the info you need from the Information Service schemas(by default stored in c:\Program Files (x86)\SolarWinds\Orion\Information Service\3.0\Schemas\). For your personal research you can use them (just read only), but it's strictly not recommended to do the modifications. The mapping between entities and DB tables/views you can find inside of <modelsMapping> element of the schema, so e.g. for Orion.Nodes go to OrionSchema.xml and search for its mapping fragments:
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