Mobile App with Database

I am looking to start a pet project to understand the building of apps with connectivity to a back end database.

I am going to start with Android as it has the biggest market share, so will be in java. I just woundered if anybody could give me some advice on the following:

1. I have read about the fact you can build hybrid apps for IOS and Android, however cannot find many positive comments about building apps this way?
2. I was intending to connect the app to a SQL DB, using a rest API to communicate with the App. Do you think this is a good approach?

Thanks for taking the time to read this, if there is any advice you think may be useful, it would be appreciated.

Cheers,

Tim