问题
when I created a new connection I find that it contains same content as the previous one, even I have not written anything to this new connection.
回答1:
A SQL Developer connection is just a session. If you use the same username as an existing connection's user you will see the objects belonging to that schema.
If you want to create a new user you actually have to create a new user. Connect as SYS (using SYSDBA connection) and
create user new_user identified by some_password
default tablespace users;
grant create session, create table, create procedure to new_user;
grant quota 100M on users to new_user;
Obviously give the user an appropriate name for your needs. Grant it all the privileges it needs. Find out more.
Once you have created the user you can create a SQL Developer connection for it.
来源：https://stackoverflow.com/questions/59230826/problem-when-creating-a-new-connection-in-sql-developer