I'm very curious about this, what were the reasons for changing between all those databases? You can't be using any advanced features if you're supporting SQL,

I'm very curious about this, what were the reasons for changing between all those databases? You can't be using any advanced features if you're supporting SQL, NoSQL and even Excel, so if you only need basic features why are you bothering with switching so much? I know of one good reason to support multiple databases, when you're writing software for several enterprise clients and each of them wants to use whatever databases their teams are used to managing.