Hi Franz,
Unfortunately there is no on-premise version of SAP NW ABAP 7.4 regardless of DB type.
You can see what is available for download from store.sap.com on following page:
Basically 7.02 and 7.03 version of ABAP based NetWeaver are available.
PS: it is pity that 7.4 basis is not available on-premise for developers. Even there are blogs out there on SCN according them seems SAP is not planning to release any new NetWeavers on-premise as trail versions for developers. Seems whole world is moving into cloud 
cheers
m./