I often use the H2 database when doing private projects, I will write how to check the H2 database on the Web.
Write the code in application.properties.
Then start the server and connect to the following URL to display the H2 database setting screen. http://localhost:8080/h2-console/
When you press the Connect button, you can see that it is displayed normally as shown below. I was able to confirm that Select works normally.