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Relation between Hibernate and MySQL in Spring Boot?

When we use JPA API in a String Boot project by extending repository class with JpaRepository and use MySQL database instead of hibernate's H2 database, I wanted to know is there hibernate still involved behind the scenes or, is it that JPA works with MySQL?
From what I have researched, Hibernate is implementation of JPA but I can't find any reference how MySQL works with JPA?

Native Queries and Audit table

I'm working with a spring project. It uses Hibernate Envers for entity auditing and Flyway for db migration. For instance If I insert values into entity that is tracked by Envers using flyway scripts (i.e native queries) does the change gets added to audit table for that entity? or should I add separate query for audit table insertion?

How to connect different databases like Mysql and oracle having same schema, table name and data in spring boot using JPA?

I want to connect 2 different database Mysql and Oracle having same schema, table and data in spring boot JPA. I've configure properties file with 2 different data sources with respective database configuration but i am stuck how to access properties of second data source.

How to map different queries for different database in one project in springboot?

In my current project, I am doing migration from Oracle to Azure SQL Server. Right now, we need to integrate both database working with same queries. Depending on what I have on my configuration, project will connect with Oracle or Azure SQL.
Problem is, there are some queries that are not compatible for both database types. For instance, nextval works for Oracle, but not with Azure SQL:
In Oracle:
... values(unique_id_seq.nextval ...
In Azure SQL:
... values(NEXT VALUE FOR unique_id_seq, ...
Therefore, I think I will need to create two different queries and my project should know which database I am loading and it should map to correct query. Is this possible to achieve in springboot? I am pretty new to springboot..
(One of my co-worker said If possible try to convert query into HQL or add the mapping entity, instead of creating separate queries., but I am not sure what this means.)

Try using Spring Boot with Hibernate.

mysql dialect in hsqldb

I'm using hibernate to manage DB operations and MySQL in my application - use org.hibernate.dialect.MySQLInnoDBDialect as the hibernate dialect. But for testing purposes I'm using HSQLDB 1.8.0.10.
I have problem with query like this (working good on mysql not on hsql):
SELECT DISTINCT(id) FROM table ORDER BY name;
I know that the problem is with distinct and order by (http://weblogs.sqlteam.com/jeffs/archive/2007/12/13/select-distinct-order-by-error.aspx ) and solution of this could be for example:
SELECT DISTINCT(id) FROM table GROUP BY id ORDER BY MAX(name);
But my question is, if there is any possibility to using MySQL dialect in HSQLDB and not have to using this solution?

HSQLDB implements the SQL Standard correctly and does not allow the ambiguous query. It is not possible to change its behaviour.
It is better to modify your MySQL queries to be standard compliant. This allows you to port your application to another database more easily.