I don't know if this is the best way to go about this but I need to create a "back-up" data extension that stores information on every email send using InsertDE.

Since a user with the same email address can receive this email multiple times over the life of the campaign I can't use the email address as the primary key. So, I found GUID() as a viable option to use to generate a completely random sequence of numbers/characters.

It's working as intended but my question is, will GUID() ever duplicate the same result?

2 Answers 2


GUIDs/UUIDs are effectively unique. How unique depends on the version of the UUID. UUID v1 are completely unique unless someone intentionally forges your MAC address (an address associated with your network card, typically burned into the network card's ROM) or if your clock resets and you get very unlucky. UUID v4 are 122 bit random variables (UUIDs are 128 bits, and 6 bits are reserved for versioning, leaving 122 random bits). The one example output from GUID() that I found was a UUID v4, suggesting that's what it tends to return.

122 bits is a lot. If you generate around 1000TB of UUIDs (specifically 2^46 UUIDs), your chances of observing a collision is around 1 in 50 billion -- you're more likely to win the Powerball lottery!

Now there have been UUID v4 collisions. This was caused by poor randomness in a specific UUID v4's generator. I do not have any specifics on how Saleforce generates their UUIDs. In theory this could result in a collision. However, in practice, functions like GUID() were designed to be used as unique keys, so it's reasonable to assume the implementation is sufficient.

In the end, the answer is "never say never," but "eventually" can mean "some time after the heat death of the known universe."


The odds of GUID generating duplicates is very very low. For practical purposes, you will not run into duplicates.

source: https://en.wikipedia.org/wiki/Universally_unique_identifier

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