Prevent Duplicate

Hello everyone

I want to prevent duplicate records being created in a field, and I know there is a lot of tutorials and videos on how to do so, but honestly its over complicated for nothing, how can I get the same system used here for email as in warning users that a duplicate already exists? I want to create a multi-tenant saas, and “Company name” must not be able to be created again not to have duplicates of the same company…

Thank you
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