Question regarding multiple copies of a game

Just wondering, if I already have a copy of a game digitally, and its on the PS4, downloaded and all; what would happen if I bought a physical disc of the exact same game and put it in?

Would it 'override' it or something, or will it replace the digital game, or will it say 'you already own this game blah blah'?

Thanks

It'll explode.

I don't know in the PS4 but in my X360 if I insert a disc it runs the disc automatically not the digital copy.

Hmmmmmm that's a good point, esp when it comes to saved game data, it isn't like the old memory card easiness of that, everything seems to be linked to digital or phyiscal, but I mean how many people have the digital version and then go and buy a physical copy, but it's a great question esp for those people.