I tried to set the Path environment variable of entering the path: "C: \ Program Files \ Java \ jdk1.8.0_101 \ db \ lib" (.jar file path) but nothing ...
I created a new variable called CLASSPATH by entering the same path and still nothing ...
How can I link this path to the compiler?
You can't set CLASSPATH to the directory where the jar files are stored; you have to specify the actual jar file by its full name.
This is a difference between a directory full of java .class files, versus a directory full of java .jar files.
So set your CLASSPATH to:
c:\Program Files\Java\jdk1.8.0_101\db\lib\derby.jar;c:\Program Files\Java\jdk1.8.0_101\db\lib\derbyclient.jar
In your particular case, since the only class you're trying to reference is
ClientDriver, which is in
derbyclient.jar, you could just set CLASSPATH to
c:\Program Files\Java\jdk1.8.0_101\db\lib\derbyclient.jar and leave
derby.jar out, but at some point in the future you might want to reference other Derby classes, such as
EmbeddedDriver, so you might as well put both
derbyclient.jar into your CLASSPATH now.