@alex1368 typically a database would prevent duplicate entries thru PRIMARY keys. You might want to check your database and configure it that way. You could also do that with a local H2 database for example. Then you might have to decide what to do if you encounter a duplicate key
You can also check in advance if your database already has the keys you want to insert beforehand and then act accordingly.
These examples might be worth exploring. But maybe you give us some more details about what you ant to do and maybe even some dummy/sample data to illustrate your point.