Does that help Whenever you face such type of error, while running Spring Boot + JPA CRUD Example, Just check once that you have defined ID field using AUTO_INCREMENT option or not. I was having such type of Error because I did not require ID field. BUT Spring Boot Hibernate checks for Unique A_I ID field. If you don't require ID field, then use and Your problem will be solved.
org.hibernate.exception.SQLGrammarException: could not extract ResultSet