What Type of Data Is UUID?

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Heather Bennett

What Type of Data Is UUID?

Universally Unique Identifier (UUID) is a standardized 128-bit identifier used to uniquely identify information in computer systems. It is generally represented as a hexadecimal string separated by hyphens into five groups, like this: 123e4567-e89b-12d3-a456-426655440000.

UUID Structure

UUIDs are composed of five groups of hexadecimal digits, separated by hyphens. The structure consists of:

  • Time_low: The first 32 bits representing the low field of the timestamp.
  • Time_mid: The next 16 bits representing the middle field of the timestamp.
  • Time_hi_and_version: The next 16 bits representing the high field of the timestamp and version number.
  • Clock_seq_hi_and_reserved: The next eight bits representing the high field of the clock sequence and variant.
  • Clock_seq_low: The last eight bits representing the low field of the clock sequence.
  • Node: The last 48 bits representing the spatially unique node identifier.

Variants and Versions

UUIDs have different variants and versions, which determine their format and purpose. Let’s take a look at some common variants and versions:

Variants:

There are four different variants defined for UUIDs:

  1. Variants reserved for future use (0x0): These variants have all bits set to zero and are reserved for future use.
  2. RFC 4122 variant (0x2): This variant has specific bit patterns defined by RFC 4122.
  3. Microsoft Corporation variant (0x6): This variant is used by Microsoft Corporation.
  4. Reserved variant (0x7): This variant is reserved for future use.

Versions:

There are five different versions defined for UUIDs:

  1. Version 1: Generated from the MAC address and timestamp. It includes the MAC address of the generating host, making it unique across all devices.
  2. Version 2: DCE Security version, rarely used.
  3. Version 3: Uses MD5 hashing algorithm to generate a UUID based on a namespace identifier and an input name.
  4. Version 4: Generated from random or pseudo-random numbers. These UUIDs do not include any meaningful information about the generating host or network, but they are unique within a given system.
  5. Version 5: Uses SHA-1 hashing algorithm, similar to version 3 but with a different hash function.

UUIDs find various applications in computer systems, such as database keys, distributed systems, and as unique identifiers for entities or resources.

In conclusion, UUIDs are standardized identifiers used to uniquely identify information in computer systems. They have a specific structure composed of five groups of hexadecimal digits and can have different variants and versions depending on their purpose.

Understanding UUIDs is essential for working with unique identifiers and ensuring data integrity in various applications.

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