In Spring/Spring-Boot, SQL database can be initialized in different ways depending on what your stack is.

JPA has features for DDL generation, and these can be set up to run on startup against the database. This is controlled through two external properties:

• spring.jpa.generate-ddl (boolean) switches the feature on and off and is vendor independent.
• spring.jpa.hibernate.ddl-auto (enum) is a Hibernate feature that controls the behavior in a more fine-grained way. See below for more detail.

Hibernate property values are: create, update, create-drop, validate, and none:

• create – Hibernate first drops existing tables, then creates new tables
• update – the object model created based on the mappings (annotations or XML) is compared with the existing schema, and then Hibernate updates the schema according to the diff. It never deletes the existing tables or columns even if they are no more required by the application
• create-drop – similar to create, with the addition that Hibernate will drop the database after all operations are completed. Typically used for unit testing
• validate – Hibernate only validates whether the tables and columns exist, otherwise it throws an exception
• none – This value effectively turns off the DDL generation

Spring Boot internally defaults this parameter value to create-drop if no schema manager has been detected, otherwise none for all other cases.