In Spring Boot 2 data.sql was not working with me as in spring boot 1.5
import.sql
In addition, a file named import.sql
in the root of the classpath is executed on startup if Hibernate creates the schema from scratch (that is, if the ddl-auto property is set to create or create-drop).
Note very important if you insert Keys cannot be duplicated do not use ddl-auto property is set to update because with each restart will insert same data again
For more information you vist spring websit
https://docs.spring.io/spring-boot/docs/current/reference/html/howto-database-initialization.html