I am new in Spring Data JPA and we have some queries in the project that using JPQL. I have SQL knowledge, but as a beginner I need to be clarified about the following questions:

1. What are the options that can be used to create query in Spring Data JPA? I see Native Query and a JPQL, but not sure if there is any other option?

2. What is the difference between a Native Query and a JPQL? I just realized that JPQL uses class names e.g. ProductCategory while native uses table names e.g. product_category. Is there any other differences?

CodePudding user response：

JPQL will be converted to SQL according to the Entities.

In SQL you write like this:

SELECT d.familyname FROM car c LEFT JOIN driver d ON (c.driver_id = d.id) WHERE c.id = 123

If you have full entities in JPQL you can use:

SELECT d.familyname FROM Car c LEFT JOIN c.driver d WHERE c.id = 123

As you can see, since the entities contains informations about foreign keys, you can shorten the queries.

CONS

The queries have limited language support, non-sql functions from postgres in example are not available.

PROS

The JPQL depends on the entites. If you change the db-vendor the JPQL must not be changed.

Other options (beside JPQL and SQL)

There is something called HQL. But I guess its compleatly compatible to JPQL, so today there is no difference.

EDIT:

You can shorten it much more using this:

SELECT c.driver.familyname FROM Car c WHERE c.id = 123