With SaaS you merely can configure (user options of) the product and everything else is managed by the cloud provider. On PaaS you can configure High Availability, Disaster Recovery, and configure options for Business Continuity, and you cannot set all this on SaaS. With SaaS you may not be able to configure options to make the product more scalable in terms of performance, as you can configure on PaaS,
If you ever take exam AZ-900, a good number of questions depend on the knowledge Azure SQL Database is considered PaaS.
We can argue that Azure SQL Database offers more than other PaaS databases offer, and because of that we should think of it as SaaS. However, Azure SQL offers a good amount of management options that are not available on SaaS.
Another thing to take in consideration is that the security of the data on Azure SQL Database is not at responsibility of Microsoft as service provider
Software-as-a-Service (SaaS) allows users to connect to and use cloud-based applications over the Internet. Common examples are email, calendaring and office tools (such as Microsoft Office 365.
