First run ij tool. The Derby ij tool is a JDBC tool that you can use to run scripts or interactive queries against a Derby database.
java -jar /Library/Java/JavaVirtualMachines/jdk1.8.0_162.jdk/Contents/Home/db/lib/derbyrun.jar ij
or if ij is in your PATH (ex: /Applications/NetBeans/glassfish-4.1.1/javadb/bin)
java org.apache.derby.tools.ij
then connect to the database
ij> connect 'jdbc:derby://localhost:1527/sample;user=app;password=app';
ij> connect 'jdbc:derby:retailpos';
ij> connect 'jdbc:derby:memory:retailpos';
ij> connect 'jdbc:derby:/Users/dev/work/workspaces/retailpos/retailpos';
after connecting you can use sql commands.
ij> show tables;
ij> select * from customer;
ij> select * from product;
to exit from ij tools
ij> exit;