How to connect multiple database in java

Question

I am working on projects where I wanted to connect multiple database to a single application it is possible or not if possible them how.

Answer 1

Primary Keys

A primary key is a field in the table that uniquely identifies the table records.

The primary key's main features:
- It must contain a unique value for each row.
- It cannot contain NULL values.

For example, our table contains a record for each name in a phone book. The unique ID number would be a good choice for a primary key in the table, as there is always the chance for more than one person to have the same name.