Re: Applying SQL UPDATE to Dataverse tables, How?
1. Because Dataverse comes from Dynamics CRM (the current model-driven apps) where there is the concept of supported and unsupported customizations. With supported customizations Microsoft guarantees model-driven apps work (because the Dataverse layer is how they intended) if they allow ALTER, UPDATE or DELETE sql statements there is an high possibility that model-driven apps stop to work, so they consider this unsupported customizations
2. "which is not realistic for developing even a silly app", if you are developing a canvas app you can use a SQL DB source directly, you don't need Dataverse, Dataverse comes with its own advantages (like the security layer and roles for accessing the data) that you will need to build in your SQL database. Canvas apps can use different data sources, model-driven apps are based on Dataverse.
3. No, there isn't another tool. Keep in mind that SQL 4 CDS converts your SQL statement to supported API calls for Dataverse, it does not execute SQL queries directly (except for the read operation if the TDS endpoint is enabled).
