# How many GUID combinations are there?

Question: How many GUID combinations are there? Answer: There are 122 random bits (128 – 2 for variant – 4 for version) so this calculates to 2^122 or 5,316,911,983,139,663,491,615,228,241,121,400,000 possible combinations.

## How many unique GUIDs are there?

Not guaranteed, since there are several ways of generating one. However, you can try to calculate the chance of creating two GUIDs that are identical and you get the idea: a GUID has 128 bits, hence, there are 2128 distinct GUIDs – much more than there are stars in the known universe.

## How many UUIDs are there?

There are officially 5 types of UUID values, version 1 to 5, but the most common are: time-based (version 1 or version 2) and purely random (version 3). The time-based UUIDs encode the number of 10ns since January 1st, 1970 in 7.5 bytes (60 bits), which is split in a “time-low”-“time-mid”-“time-hi” fashion.

## How many unique UUIDs are there?

Each character can be a digit 0 through 9, or letter a through f. 32 hexadecimals x log2(16) bits/hexadecimal = 128 bits in a UUID. In the version 4, variant 1 type of UUID, 6 bits are fixed and the remaining 122 bits are randomly generated, for a total of 2¹²² possible UUIDs. We’ll refer to this value as n.

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## What are the chances of a GUID collision?

Likelihood of Collision

Assuming a perfect source of entropy on each device generating random GUIDs, there is a 50% chance of collision after 2.7e18 random GUIDs have been generated. That’s more than 2.7 million million million. That’s a lot.

## Can GUID be duplicate?

Theoretically, no, they are not unique. It’s possible to generate an identical guid over and over. … From there (via Wikipedia), the odds of generating a duplicate GUID: 1 in 2^128.

## Should I use GUID as primary key?

GUIDs may seem to be a natural choice for your primary key — and if you really must, you could probably argue to use it for the PRIMARY KEY of the table. What I’d strongly recommend not to do is use the GUID column as the clustering key, which SQL Server does by default, unless you specifically tell it not to.

## Is UUID same as MAC address?

UUID is a 128-bit value used to define IDs that are unique in a variety of implementations, such as code objects and hardware parts. … MAC address is the 48-bit ID of the Network Interface Controller (NIC) used on the network to identify the physical network card. For obvious reasons, they are supposed to be unique.

## What is the difference between UUID and GUID?

UUID is a term that stands for Universal Unique Identifier. Similarly, GUID stands for Globally Unique Identifier. So basically, two terms for the same thing. They can be used, just like a product number, as a unique reference for an academic standard or content title.

## How do I generate a GUID?

Mapping the components to a GUID

1. Convert the name into bytes. …
2. Convert the namespace into bytes. …
3. Concatenate them and hash using the correct hashing method. …
4. Break up the hash into the main components of a GUID, timestamp, clock sequence, and node ID. …
5. Insert the timestamp component into the GUID: 2ed6657de927468b.

## Can I use UUID as primary key?

UUID values can be generated anywhere that avoid a round trip to the database server. … By using UUID, you can generate the primary key value of the parent table up front and insert rows into both parent and child tables at the same time within a transaction.

## What does UUID stand for?

Universally Unique Identifiers, or UUIDS, are 128 bit numbers, composed of 16 octets and represented as 32 base-16 characters, that can be used to identify information across a computer system. This specification was originally created by Microsoft and standardized by both the IETF and ITU.

## What is Type 4 UUID?

What is a version 4 UUID? A Version 4 UUID is a universally unique identifier that is generated using random numbers. The Version 4 UUIDs produced by this site were generated using a secure random number generator.

## What does a GUID do?

(Globally Unique IDentifier) An implementation of the universally unique ID (see UUID) that is computed by Windows and Windows applications. Using a pseudo-random 128-bit number, GUIDs are used to identify user accounts, documents, software, hardware, software interfaces, sessions, database keys and other items.

## Is GUID NewGuid thread safe?

You are concerned with concurrency: fortunately, the NewGuid method is thread-safe, which means it either locks or utilizes a thread-static random number generator for its purposes. … Static methods of Guid are guaranteed to be thread-safe.

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## Is machine GUID unique?

The MACHINEGUID is the unique identifier for each client machine. Therefore if there are duplicate MACHINEGUID entries, machine entries in the Encryption Management Server database will be constantly overwritten.

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