User Accounts - Same user signing in with different social networks

I’m developing an app that supports local authentication plus 3 external authencatications: Facebook, Google and Twitter. I already tested all those methods with my personal accounts for each method and when I went to query the users table, I noticed that there were 4 different user entries all with the same email, is there any way to maintain just one entry for each email and login in the same user account independently of the authentication method used?

Any help would be appreciated.

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