Spring data jpa. Find max if no result return default value

问题

I've implemented in my spring repository interface:

@Query("SELECT max(ch.id) FROM MyEntity ch")
Long getMaxId();

It works correctly if db is not empty. If I start my environment with test configuration (H2DB is used) - there is no data in the very beginning. And result returned by getMaxId() is null. I would like to have here 0.

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Is it possible to modify my *JpaRepository to have 0 result? If yes, how it should be modified?

回答1:

You can use coalesce like :

@Query("SELECT coalesce(max(ch.id), 0) FROM MyEntity ch")
Long getMaxId();

If there are no data it will return 0 instead of null.

来源：https://stackoverflow.com/questions/44723744/spring-data-jpa-find-max-if-no-result-return-default-value