View source for GUIDs, UUIDs and the Need for Unique Identifiers

'''Summary:'''
Globally Unique Identifiers (GUIDs) and Universally Unique Identifiers (UUIDs) provide a mechanism for uniquely identifying objects, records, and resources across systems without requiring a central authority.

== Context ==

Almost every computer system needs a way to uniquely identify things.

* Users
* Documents
* Orders
* Projects
* Devices
* Events
* Database records

=== What is a UUID? ===

UUID stands for:

<pre>
Universally Unique Identifier
</pre>

A UUID is a 128-bit identifier designed to uniquely identify an object.

=== What is a GUID? ===

GUID stands for:

<pre>
Globally Unique Identifier
</pre>

GUID is Microsoft's terminology for a UUID.

In modern systems, a Microsoft GUID is typically a UUID Version 4.

<pre>
GUID ≈ UUID v4
</pre>

== UUID Versions ==

=== UUID Version 4 ===

Advantages:
* Simple
* Widely supported
* Difficult to predict

Disadvantages:
* Not time ordered
* Can fragment indexes

=== UUID Version 7 ===

Advantages:
* Time ordered
* Database friendly
* Efficient indexing

Disadvantages:
* Approximate creation times can be inferred

== Conclusion ==

GUIDs and UUIDs solve the problem of uniquely identifying objects without central coordination.